Theres a lot of talk over on CG talk re the gforces, they seem to work fine when you adjust some settings, I personaly have never had a problem using them from the 4XXX series up to the 8XXX series.

I did have problems with some older radions 1300 and 1600's they were rubbish, textures didnt display correctly, no HQ rendering or shadowing etc. The new one I have the 4800 is perfect. Also Ive never really seen much/any of a difference between the quadros and the Gforces/radions when it comes to maya, only maybe texture display.