People get very defensive about Linux - it's free so it has the moral high ground in terms of software.
The problem with Unbuntu is that it's effectively a wavefront development. If it's really well managed, it can be done. Ubuntu isn't well done. Sure it's "user friendly" in that it has a nice interface (although I didn't like Unity when I tried it after installing 11.10) but it has problems. Specifically, newer hardware tends to be less well supported, manufacturers tend to have a lower priority to Linux drivers - and the nether regions (for example the hibernate sequence) is down to pot luck as to whether your driver set works well enough to enable it. I'm on some mailing lists where people have had to debug hibernation issues and you get comments like "yes, hibernate works, but you have to unload the driver before it will hibernate properly and then reload it on the resume". That's what I call off piste
Precisely
because there is so much choice, it becomes impossible to test it properly. As I said, I tried Unity when I installed 11.10. I didn't like it but the main reason for the box was as an embedded xbmc player. Downloaded xbmc, installed it, played a video and there was screen tearing. 10 minutes googling and it's a known problem - Unity window manager (more precisely compiz which it is the underlying WM) causes tearing on video playback. Known bug, been there for ages, but presumably the people who develop compiz don't do much video replay so it hasn't had much attention. The solution - switch to another window manager! And should you ever mention to a developer that perhaps this was an important bug, you typically get the "patches are always welcome" style response i.e. if you want to fix it, be my guest and let us know how you've fixed it when you have done. Or to put it another way, you get what you pay for
I've only scratched the surface of the UI as most of the stuff I do with Linux/Unix here is command line or running a complete environment where someone else has tested things - e.g. xbmc. There, it works beautifully (although you might have more massaging to do to really get it to work) but you will probably need to get closer to the metal to do it. Every time I do use the windowing interface, I find more bugs than I'm happy with so end up dissatisfied with the experience/
If people really want to use Linux, I'd actually suggest a distribution which changes less frequently than ubuntu. In fact, I'd probably suggest using a BSD variant rather than Linux. My experience there has been much more positive....