What do those who have installed SolidWorks under Bootcamp on a Mac recommend for the Windows partition size? If I have a 500GB drive, would you set it 50/50, or would you cut down the Windows partition size? What works best?

Also, for a new install (onto a new Mac) should I opt for Windows 7 (which is out in a day) or take the XP or Vista route (OK maybe not the Vista route). From what I've read about Windows 7 it seems to be everything Vista should have been, and better than XP. Or am I just kidding myself?