I tried out Unity which is going to be the user interface for Ubuntu 11.04. It's built on top of GNOME, and it's currently used in Ubuntu's Netbook edition. Overall, I liked it. It's definitely one step closer to OS X. For instance, menus are shown at the top of the screen rather than at the top of each window. Unfortunately, I encountered several bugs when trying to use an external monitor, so clearly Canonical's programmers have their work cut out for them to hit Ubuntu's 11.04 release (due in April, of course).