I ran linux on the desktop for 4 years before getting my iMac. I'd have to say Ubuntu and kubuntu (surprisingly kde runs better on ubuntu than gnome) was the best distro for desktop that I've used (started using Ubuntu when it first came out) I also second looking at distrowatch.com if you're trying to find a distro to use. (although your right, catagorizing would be more useful).
A Mac User Tries Linux Part 1