I have run EQ in Vista on a variety of hardware. It works great. Alt+Tab'ing between EQ and IE or other programs even seems to make it crash less often than it did on my XP machine.
You do have to jump through more hoops to make EQ work initially in Vista, but once it's working you're good to go. For example, you may initially be missing some DirectX 9 components that EQ wants but does not re-distribute itself, so one of my first stops on a new Vista PC is the DirectX website. To get the new launcher installed, you may have to do a few things manually since UAC can break the new launcher's installer (though they may have fixes that since I last tried).
I have not run EQ in a 64-bit OS, but running a 32-bit app in 64-bit Windows is nowhere near the nightmare that a 16-bit app in 32-bit Windows was.