QD I run Ubuntu on both my custom built PC that is five years old and on my EEE PC 1000hd laptop. It really does run faster than Windows. My only issue is moving from the software I use. Going from photoshop to GIMP really was a downgrade - I don't like it as much. There is a slight learning curve, but if you know how to use google and read you'll be able to find guides to help you with anything. Overall, I really like Ubuntu. The latest update, karmic koala (9.10) is working nicely for me and it looks better than Windows IMO.

Also - to comment on the issue of software raid controllers - I would suggest using hardware controllers. Like previously stated, software ones sometimes fail.