Just my thoughts on Vista here. The biggest problems seem to be with installing it as an upgrade over an existing system, with poor drivers for the 64-bit version, and poor drivers for old hardware. I tried to upgrade over my 3 year old XP installtion and it failed miserably. Reformatted and installed from scratch and it works perfectly. I doubt you'll have serious issues on a pre-installed 32-bit system.

I'm not sure how EQ handles using multiple cores, but I know WoW does not use more than 2 unless you tell it to, so that is worth looking into to make sure you get the most of it.