Mossblaser has uploaded a stunning UI design concept for the upcoming Ubuntu release. I hope the Ubuntu folks take note, as it is nicely polished and in line with what the other competing operating systems are doing.
On the design discussion thread someone was moaning about the font choice making the interface look un-Linux like. Personally I think that's one of the best improvements of the design. The default Linux font is just plain icky, and in my opinion, anything that makes the operating system look less like Linux is probably going to improve the adoption rate amongst people who are used to other commercial operating systems (you know, those than can afford to pay professional graphic designers).
Ubuntu 8.04 GUI Design Idea