Ubuntu only works until.....it doesn't and then you actually have to put your thinking cap on. In some ways its really great for new users since most things work out of the box and hardware detection is great. You could thank the Canonical software engineers for this great feat.
The negative however is that the default user probably doesn't have a clue of what's going on behind the scenes and then gets frustrated really easily when things don't work. This wouldn't be an issue for example if they had set their system up in the first place with more of a manual rather than automatic method.
A big difference in the various distributions other than desktops or window managers and stable vs cutting edge packages, is how much "hand holding" they do for new users. Ubuntu and Mint are two very popular distributions that attempt to do most things automatically. Gentoo on the other hand does nothing -- everything has to be configured manually.
In my opinion,once your fairly comfortable with Ubuntu, its always a good idea if you have another computer laying around or with use of VmWare, to try other distributions. I recently installed Arch on a spare laptop someone gave to me -- it was a used 4 year-old laptop a big corporation thought had no more use. Arch really doesn't offer me anything more or less than Ubuntu, but I've really grown in my knowledge of Linux in general about troubleshooting problems, since Arch requires a lot of user interaction and configuration during installation. It's actually helped me learn Ubuntu a lot better in terms of troubleshooting various problems and with kernel tweaking.