I have an FIC 503+ running at 412 Mhz and I have been running a Visiontek Geforce256 SDR for a couple of months.
I wish I could say I have had no problems but it is not true. On the otherhand, I had problems before I got the Geforce.
I used to get spontaneous reboots but somewhere along the way between Windows 98SE reinstalls, multiple Detonator driver (geforce drivers) updates, Bios updates, adding, removing, adding again various tweaks the problem went away.
I still get occasional system crashes but not usually while playing games.
Direct3d games work best with no crashes that I can recall. However, I would have strange experiences with OpenGl. Whenever I reinstalled the drivers,(I have found detonator 6.31 drivers to be the best. 6.47 slowed down performance considerably), things would seem to work fine for a while. Then one day I would have crashes in Half-life and the problems wouldn't go away until I unistalled and reinstalled the drivers. I could still run the game using the Direct3D driver. (I leave Half-life in that mode).
Recently I found some tweaks to the Windows registry that seem to have fixed my OpenGL problems. The "tweaks" can be found at www.3dspotlight.net/tweaks/tnt-geforce. They are intended for geforce users who have Super7 motherboards.
After I purchased the geforce256 card I read, somewhere, that it was probably not a wise choice for a Super7 motherboard because it consumes too much power. For this reason the Geforce2 cards are a better choice. You should also have a 250 watt power supply or better, in any case. Mine is only 235 watts.
I can't tell you if the Geforce is causing me problems any longer or if my FIC 503+ is unstable or what.
I can tell you that the Geforce works great when it is working. As I said I don't seem to have any problems with Direct3D games.
Good luck.