I used to use GeForce cards exclusively for MAME etc using soft15khz on low res monitors but when I came across groovymameand calamity's ATI drivers I picked up a Radeon HD 3850 and never looked back.
The great benefit of these drivers is with MAME you can get accurate refresh rates meaning no tearing/sound skipping which requires some fairly intrusive work arounds using soft15khz. Otherwise they are the same as soft15khz but support much more powerful cards without the need for an EDID dongle.
They are both still actively being developed, support some powerful cards without the need for extra hardware and the support forum is great too and calamity is a really friendly, helpful guy.
For the record I've had better luck with this card and PC games/Emulators requiring 3D accelleration than my old GeForce 7xxx series card.