Trans-Am makes a good point. The SLI advantage that Nvidia has, is a considerable one. As of right now, you'd need to spend mucho dollars on a compatible Motherboard (2 pcix16 slots) and 2 pcix 6800 GT's or Ultras. Right now, it doesn't make sense for any but the elite few rich people that spend a lot of time playing Doom3. For the rest of us, the upgrade path that SLI offers is very attractive.
Ati has stated their version of SLI to be pending, but NVIDIA has a track record here. I can't argue against ATI, because their cards are excellent as well, but truth be told... I've got Nvidia 6800 in my machine. (or, at least I will when my card comes back from RMA, for now the old GF4 MX makes a triumphant return )
