I have run various flavors of Linux over the years, Ubuntu is still my favourite. SimplyMEPIS is quite good, it handles drivers particularly well, i didnt have to do anything special to get my preferred TwinView set-up going, which usually sees me fiddling for a while with xorg.conf with Ubuntu.

Its not really mainstream yet, and I like it that way, though my mother can use Ubuntu for basic web surfing and word processing without any issue once the machine is set up.