I'm using XP x64,Intel Q6600 Quad core, Nvidia(XFX) 8800 Ultra(768 on board ram) with 8g of system ram.

My machine is running like a sewing machine and very very stable.  I get no more OOM's with Vue & can jam pack a scene.  I have yet to go below 85% resources. There are still other bugs, but no more OOM's.

I only had 2 programs I couldn't install to x64.  One was an old KPT(version1) plug for PSP and Kodak Easy Share for my camera(which I don't need anyway).

The only app that has issues is Shade x64 version.  If Windows has an update I have to reinstall the video drivers - this is a known issue.

Anyway - I recommend XP x64.