Ubuntu/Debian's package management (Aptitude) usually receives better praise than RPM-based management, and as Geoff pointed out, just apt-get install <name> to install the software and its dependencies.

There's nothing wrong with Ubuntu at all, and you can download versions tailored for Gnome (Ubuntu), KDE (Kubuntu), and XFCE (Xubuntu). Or if you already have it installed, it's just a matter of apt-get install [x/k]ubuntu-desktop to install KDE or XFCE respectively.

SUSE has changed a lot with Novell's involvement, and they have done a lot in the way of usability studies and (I believe) contributing to the Gnome desktop environment and getting linux into corporations and governments around the world.