Linux Mint ( http://www.linuxmint.com/ )
It's based on Ubuntu, so guess how smooth it can be to install and run. :)
I've installed it on 4 or 5 computers yet and I've been surprised about how many drivers I had to care about (one in fact.. on 4 PC...
Linux Mint :D
I have tried ubuntu, kubuntu, studio ubuntu, stoner edition and Linux mint has been the most stable Os i've tried. I really want to try debian and others. Or the desktops xD especially Beryl.