Just wanted to add a few thoughts about why Ubuntu and Unity are really working out for me. Perhaps these points aren't all that interesting, but I thought it would be worth noting how what might be miffing power users is really helping me make a pretty major leap to Linux.
I'm responsible for making computer decisions for a small business and have just begun a transition of our desktops from Mac/OSX to Ubuntu. I'm switching, or at least plan to phase in, 15 new desktop computers over the course of the next 18 months.
In full disclosure: I have not been able to develop a religion about any of the Linux GUI's out there. I have run and configured desktops with XFCE, KDE, Gnome 2, Gnome 3 and Unity (and even E17, with Bodhi Linux). I like aspects of all of them, and probably prefer KDE on a good-size display.
When I was planning the move to Ubuntu, I spent time with Unity and think it's the best way to go for a few reasons.
1) It's definitely going to be the smallest learning curve for my office of OSX users. The desktop is different but everything from the launcher to to the system tray and notifications are in places my users will feel comfortable with. this is probably half the reason a lot of other long-time linux users dislike Unity. Believe me, I'd love a lot more customization control. One reason KDE is a non starter is that I know my users would not be able to figure out why they couldn't simply move files to and from their desktops the way they're used to. Unity retains that. Of all the actively developed GUI's I really think its the easiest for newbies to use. Put the applications they need in the launcher and send them on their way.
2) Ubuntu;s resources, from the community to Canonical's polished website made it easy for me to convince my company's bosses that it was a good choice. The polish of Ubuntu helped me convince skeptics that we weren't going to be adopting some hobby OS. This is less about Unity GUI features than the fact that it is the desktop of a really polished and functional distribution.
3) In testing out Ubuntu, Nautilus is able to connect to our Mac OSX server, browse and copy files out of the box. I couldn't get the same functionality out of Dolphin in KDE. That doesn't mean that Dolphin wouldn't work, Nautilus just worked better. I could have used Nautilus in KDE , but it would have required extra configuration.
4) Finally, the ideal GUI for me wild merge KDE and Unity. The keyboard shortcuts in Unity are my favorite feature. I can get a lot done, particularly on a little laptop I have, without going to the mouse all the time. I understand why people would like to keep their applications organized int he old pull down menus, and the Dash could be A LOT more useful, but I think it's coming along. I really like what I'm reading about the current state of Unity 5.2.
Nothing revolutionary here, but Unity is a pretty big part of my office making a major OS transition. Would it have been possible with Gnome 2 or KDE? Probably. But Unity and Ubuntu are definitely going to keep the people in my office pretty happy.