Quad SLI was really less of a disaster than I thought it would be, considering just how early in the game it is. Vantage scores are simply jaw dropping; we don't doubt for a second that come a few hours after the NDA lifting that the world records in 3DMark Vantage would have been broken.
It also doesn't come as a surprise that games that don't take advantage of SLI (like PT Boats) don't see a boost in performance. It's a bit disappointing to see the source based Left 4 Dead get impacted negatively in a quad SLI configuration, but this game has been quite important for NVIDIA so we don't doubt that they're going to fix this issue.
We weren't going to see gains of 100%; it just simply never happens. We do, however, see some good gains around the 40% mark at the highest resolution. What this performance increase will let you do is start to turn AA and AF on at 2560 x 1600 under these newly released intensive games like Far Cry 2.
Quad SLI isn't for everyone, purely from a cost perspective, but unless you have a monitor that is out putting 2560 x 1600 it really is a complete waste of money with this resolution seeing the best gains.
Considering Full HD is considered as 1920 x 1080 and HD gaming is something that the big two have been pushing lately, this setup could really be marketed as "Gaming beyond Full HD" with it making 2560 x 1600 gaming not only playable, but pleasurable.
Quad SLI isn't perfect and it probably never will be, but we love it so much and accept it into our lives with open arms. If you've got the money to afford it and the monitor that can take advantage of it, you won't be disappointed.