My gaming PC (an Alienware laptop) uses Windows 7 Ultimate, and my netbook (an Asus t101mt) uses Ubuntu 10.10 with an upstream kernel (2.6.38). I wouldn't have it any other way, Windows is great on the powerful computer and works well with the large screen. GNOME, with its workspace system, is amazing on the netbook for multitasking without feeling cramped, and Ubuntu runs crazy fast even on an Atom processor.
Different systems for different purposes.