Installed Doom 3 last night on my PC running Vista Ultimate 32-bit.
Runs flawlessly, and I am achieving good frame rates (although I
noticed some jerkiness during intense battle scenes when Windows
Defender kicked in).

Definitely an entertaining game with stunning graphics -- I have it for
my Xbox too, but I finally came to the conclusion that I think I prefer
a PC with a mouse and keyboard for first-person shooters.

I was almost surprised. With all of the horror stories floating around
regarding Vista's alleged bad software compatibility track record, one
practically anticipates things not to work at times. However, most of
the software that I've attempted to install under Vista has been
cooperative -- I've only run into compatibility problems in a small
minority of cases.