I'd like to throw out a very important disclaimer. What I'm about to discuss in this thread is entirely my opinion. Nothing in this thread is deemed in any way shape or form a hardened fact. I will be throwing some comparisons on the table, but they will be based entirely from an opinionated standpoint with my own experiences.
Years ago I caught wind of Gnome 3.0 hitting alpha state. I fired it up and began to use it. I was so anxious to use something new that I was pretty much giddy about it, so naturally my opinion was extremely high at first. As time progressed (as in, almost immediately within the following days), I began to feel absolutely enraged at the terrible use of this so called "new desktop paradigm". I realized I was taking longer to accomplish certain tasks. Even finding an application was a slow and cumbersome experience. I ended up ditching it and joined the unofficial Gnome haters club.
Since then, I have flirted with many other desktop environments. Naturally, Unity was a continual contender for top place as I began to use it more and newer versions of it came out. It was turning into a very smooth flowing desktop environment to use. I had one problem with Unity, though... I love using an environment that is available on other distros. The reason behind this is in case, someday, for whatever reason, I decide to go with another distro, I can still have a familiar environment, such as with openSUSE, Fedora, Debian, you name it, the list goes on. With Unity, there's Ubuntu, and it doesn't go much further than that. I began to sideline this idea, but after recent versions of Unity came out with certain lenses and 'features', I discounted the environment all together and decided to look further.
This is where KDE came in. At this point, I had used Gnome 3.0-3.2ish, Unity, and now KDE. As a result, I felt myself growing more familiar with the 'newer' desktop paradigms to the point that I actually preferred them. That's why I won't be mentioning XFCE here, as XFCE is more of a traditional paradigm. Don't get me wrong, we use XFCE here at work on quite a few systems (soon to be just over 3,000), and it's a fantastic environment to use and I give the devs all the credit in the world, but as I said, I just began to prefer newer paradigms for my uses. Anyway, back to KDE. I found the Homerun launcher, which mimics the Gnome/Unity feel very nicely. In newer additions of KDE, it's a widget that's built in and available by default. Just need to add it to the panel and you're good. Homerun is a fantastic launcher, and for me in particular, a must have with my KDE usage. Like continual instances in the past, certain things began to wear on me with KDE. While I was very impressed by the speed increases brought to the table with KDE 4.10, I feel as though there are, somehow, still too many half baked edges with it. Sure, there are a tremendous amount of features, you can switch themes and icon sets borderline instantly, but certain things are a catastrophe. For one, I cannot stream videos over Samba from my server. It's a 3 year old bug that has yet to really gain any traction. In Gnome/GTK based environments, thanks to .gvfs, this is (and always has been) an effortless task. The color schemes of KDE don't exactly appeal to me either, as sometimes I feel like I'm in a weird cross between a plastic reality or some sort of anime. I know, a little thick, but it's just my 2c. Along with that, I always felt like the panel was rather rough. In particular (this is going to sound incredibly nit-picky), the clock has always bothered me. There seems to be a lot of empty space around the clock text, and since the clock text scales based on the thickness of the panel, I find myself having to have a rather thick panel just to bring the clock text into an "easy-to-read-at-a-quick-glance" state. Each time I use it, I just look at the clock and think, such a minor thing, but... why doesn't it make better use of the available space? The other day I installed KDE 4.11 to see what was new, but what I didn't expect to be new was a handful of rather obvious bugs. KDE 4.11 crashing because I changed the time is something that truly does make you wonder. That's like Ford forgetting to put front tires on a new vehicle that just left the plant en route to a car lot to be sold. I know, I know, it'll be fixed in no time, but still... if nothing else, it makes you raise an eyebrow in confusion. I love so much about KDE, but there are enough small things on the radar to make me consider alternatives, particularly due to the Samba streaming issue I outlined above (that's a deal breaker right there). So anyway, KDE... overall it's absolutely awesome, but a few personal pet peeves. Don't hate me, just my opinion.
So now... we're back at Gnome. At this point, Gnome is at 3.8. Beginning with 3.8 is where I really started to appreciate Gnome in its entirety. Feeling almost exhausted with trying out different environments, I decided to just cut loose and disconnect from what I do or don't care about, and just USE Gnome and see how the cards fall. After a while, it clicked with me. Gnome is actually... pretty awesome! I found myself using it at work on all of my systems. Once you get the hang of the flow, the efficiency really is decent. Dynamic workspaces are very handy, and the activities overlay is very presentable. Beginning with 3.8, you can no longer scroll over windows in the overlay to zoom them in/out, but now scrolling gets you up and down the dynamic workspaces. Since 3.8 makes better use of placing the window thumbnails (they're larger by default than they were in 3.6), this turns into a non-issue, in my opinion. This intrigued me to use workspaces more, and I'm glad I gave it a solid chance. Couple that with keyboard shortcuts to move to other workspaces without having to hit the overlay and you have even more efficiency at your fingertips.
Another absolutely killer feature of Gnome is the notification menu. It's brilliant. I know I'm sounding like a cheerleader, but it's been a treat to use. Say on Empathy, I get an instant message. If I am actively using my computer, a notification will show up and stay at the bottom/center of my screen for about 3 seconds. If I am idle, like I went to go make some coffee, when I come back it'll still be on my screen. If I move the cursor, about 3 seconds later it disappears. Likewise, I can click on the notification window that comes up, bringing me to a full instant messaging menu. OR, I can hover over it, bring it up large enough with a text box to click in the text box and respond back. I can effectively do all of my messaging without coming into contact with Empathy. Of course, if you want to view your buddy list or start a new message, Empathy's native instance is needed for that, but for quick messages already existent in the messaging tray, this is really nice. Likewise, if you're a keyboard centric user, you can super+M and bring up the notification bar, at which point you can click on which item you want or use the arrow/enter keys in a similar sense.
Another nice feature is thanks to evolution-ews, which is a package that allows your Evolution application to integrate with Exchange services. Since we use Exchange here at work, this is a nice bonus. It will pull in my calendar, contacts, tasks, email, etc. My calendar entries also get synchronized to the calendar widget that drops down if you click on the clock in the top/center of the screen. This makes it super handy to quickly see what you have going on that day. Evolution, admittedly, can be a little finicky now and then. Once every few days I find it being a little sluggish with syncing in new emails, but closing and reopening fixes that. I have no explanation for it, but considering the level of integration that's available, it's a minor quirk I'm willing to live with.
In terms of the overall UI, it is extremely polished. I'm going to throw some more sticks here, so please don't hate me, but my clock... it's readable! I have a really thin panel at the top of my screen with my clock there, and it is extremely easy to read and makes great use of the available space in the panel. All of the applet indicators follow suit, as the level of contrast and their relative spacing makes them very legible to see at a quick glance. Recently I began tinkering with the newly released Elementary OS, which is largely GTK based. I noticed there too that things were very clean and readable. Cinnamon follows a similar path. I'm starting to question if the capabilities of GTK are just easier to deal with in terms of achieving UI polish. Sure, desktop effects are nice, aero-like blurred edges are a bonus, but that's not what "really" matters at the end of the day, at least in my opinion. I'm sure some toolkit developers reading this are rolling their eyes at this point because I'm sure that's not the case, but I'm just throwing a very generalized and likely inaccurate opinion on the table based on what I've seen as an end user. On top of that, the available extensions for Gnome allow you to tailor the system a bit. If you prefer having your left overlay dock available at all times without going into the activities menu, there's an extension for that. I have a few select "must have" extensions, such as weather, system monitor, sensors, and media player indicator. Lately I have been using dash to dock (as mentioned a minute ago), which I am liking, but not finding it overly needed. However, I know that some users absolutely swear by this extension, so I'm very happy to see it exists.
One frustration I have had with Gnome is the lack of themes that are readily available. I actually had a lengthy discussion with Gnome developers about why this is, as I was concerned by the lack of themes that were available. It sounds like the general stance on this topic is earlier on, Gnome 3.0 did not have full CSS compatibility, which allows a high degree of leniency when creating a theme. As newer versions came out, this area grew a bit stricter to follow suit with CSS guidelines, which essentially broke "compatibility" with some themes. At this point, CSS compatibility has been seemingly achieved, so now theme breakages from one version to another should be a non-issue. I cannot speak from a factual standpoint on the topic, but this discussion with several Gnome developers gave me hope that this is an issue of the past. I will give KDE some strong props in this area, though... installing themes and icons could NOT be any easier than the way KDE currently provides. That's a very well done feature.
Different desktop environments suit different personalities. We're all different and have dissimilar habits, preferences, etc., which is why it's so awesome that all of these environments exist. If you are a KDE user and enjoy it, congratulations - that's awesome. If you use Mate, XFCE, LXDE, or whatever else is out there, by all means carry on with what is working best for you. I think part of the reason why I wanted to post my experiences with Gnome is due to the frequency of users I speak to that clearly have not used it for more than 12 seconds but have a very bold stance against it. If you are a user that has used Gnome extensively and decided that it wasn't for you, I give you all the props in the world for at least trying it. Unity went through a similar course in relatively recent times, as people were jumping ship left and right to get away from Unity, and now users are coming back and seemingly enjoying it. That's awesome... that's software evolution at its finest.
Bottom line is, use what works for you. After all... I do.