Several of my colleagues have the Dell Inspiron 8100 with Geforce 2 Go. I had the Dell Inspiron 5000e with ATI Mobility 128 card (slow). Now I have a iBook.
I don't want to rain on your parade, but I can't say I'm overly impressed with the 8100 setup:
1) It's huge.
2) nVidia's graphics drivers are suck when using the VGA port. Knowing what I know now I'd rather have a slow ATI card than a fast nVidia at this point. They really need to work harder on their laptop drivers. If you don't use the VGA port however, then they're fine.
3) The Firewire port is 4-pin and non-powered, which essentially defeats the point of a Firewire port IMO. Firewire ports should be 6-pin powered ports. (For instance, my Lexar Firewire CompactFlash card reader draws power from the Firewire port. It won't work on an 8100. Neither will many external portable 2.5" drives, or an iPod, etc.)
4) You can only get the ATI card with the monster sized 15" screen. I doubt I'll ever buy a laptop with 15" screen again, unless it's still ultralight.
ie. Depending on what you're looking for the 8100 might be fine, but if you really want an all around machine, I'd look elsewhere. Or if you decide you don't need all the "features" the 8100 claims to provide (but only does so in a half-@ssed manner), I'd save your money and get a model with "less" features.