Well, Ubuntu has a pretty straight forward gui. I mean all distros have a pretty straight forward gui to begin with. It is all about what you want to do with it. There are programs like
Compiz fusion that allow you to have 4 desktops on a cube, and switch between them. So have a look at different distros, like
Ubuntu, or
Fedora Core 9. Those are the two most prominent, distro.
Cheers!