As stupid as it may sound, WinXP is just fine with me. No sound driver issues, better performance, smaller installs, compatible with all the hardware I've bought over the past 10 years.
I've got three versions of Cubase (3.7, 5.1, and Cubase 4) that'll run just fine on XP, as well as Waves plugins and a myriad of other software.
For the "music machine", there is absolutely no reason for me to upgrade. Which makes me happy.
Once I get my other projects out of the way I'll be looking into Ableton. Seems to be a fantastic program.