I've recently tested the three distros (Ubuntu 8.10, the latest stable Debian and OpenSUSE 10 or 11, can't remember now).
* Ubuntu was the most usable "out of the box" (better menus, cutest colours,etc).
* Debian has the best package management / repositories, etc.
* SUSE has the best desktop experience, after you put some order in that mess of menu system they install by default.
I tried all three systems with Gnome.