I recently installed ubuntu 7.04 on my comp. I like it, and I think it's nice, but I wouldn't use it as my primary OS because, for one thing, it can't run a lot of things that Windows can unless you buy a third-party program like Win4Lin. And also I'm not used to the command-line interface that you have to use for installing programs.
Also my friend had major problems getting Ubuntu to work with his Wifi card.
On the other hand, Beryl is freaking awesome.