Shit just hit the fan! GTX680s are out on the market. That is if they aren't sold out anywhere :P
With performance like the chart below, one of these 680s challenges 2 560Ti 2GBs which is pretty impressive, though it is exactly double the price of a 560 for one 680, it's half a dozen of one and six of the other really. The framerate is basically identical to two 560s
If I'm not mistaken though, you can run 3 monitors from one 680 versus 2 of almost any other card in the nVidia line up. The only real advantage to the single 680 is less power consumption so you wont have to up the PSU much to get the performance you want.