Radoen and Geforce cards have two slots, older TNT's, and ATI Rage cards would be out, I think my Matrox G400 is out as well?
I can?t believe Intel would not use a universal PCB (like MSI did with their 694D), after all it is a 1.5v. I would think many would not buy the i850 because they can?t use a V5, rather then the other way around (just my guess).