I didn't mean to scare you away from SLI... as a matter of fact, I now regret, a little, that I didn't get an Abit SLI board and two 7800 GT's. I would have had to buy a stronger PSU, but I just decided to get a better one for my second machine, so it would have worked out okay had I gone SLI. My case is already a noisy wind tunnel, so increased noise wouldn't have been a problem for me. It's probably a little silly for me to be more concerned about SLI driver issues, as there are always driver issues with certain games.
If you're starting completely from scratch, you just might want to spend a little more now for SLI. If you're upgrading and want to use a marginal power supply which really isn't strong enough for a loaded SLI rig, and want to keep the fan noise low, you might not want SLI.
Again, I have no first-hand experience with SLI, so take my ramblings as nothing more than a little food for thought.