I installed the 32-bit Ultimate edition of Windows 7 on my laptop last night. The laptop is a Toshiba Satellite L35 series manufactured in 2006. It has a 1.6GHz Intel Celeron M CPU with 1.5GB or RAM.
It runs GREAT!
Startup time from power button to ready is about 2 minutes, 10 seconds. All programs launch quickly and there is no delay in switching windows, minimizing/restoring, etc. I am suitably impressed.