I use a forensic OS for work, which is (slightly) based on Ubuntu, and I have a tower which runs Vista. No lie, the thing hasn't crashed, frozen, blue screened or anything, ever, and it gets daily use for word processing, media, internet access... I feel like complaining to Windows that it's in someway broken. I haven't had the full Vista experience XD.
Oh and I also use Mac OS X Snow Leopard on my laptop occasionally.