Gigabyte made the whole SLI package on one PCB. Instead of having another piece of hardware connecting 2 different video cards, its on the same PCB. Check out Anandtech, they have anice review of it.

No need to get it. The 6800 ultra still wins, 2 6600 cards are almost just as fast (Gigabyte OCs their cards a bit), and you lose the option of having 2 DVI ouputs if you ever need it since its all on one card. It has 128mb of RAM for each GPU, not shared and the 256bit is also shared so its only 128 bit each. They causes some problems with AA/AF since they are so memory intensive. Thats where 2 real 6600 cards win.