In terms of $

erformance, it most certainly isn't.
I'm man enough to say that my purchase of a 690, 7970, and three 670s is not based on a carefully calculated cost

erformance analysis. I'm fucking crazy, and that's okay.
For people aiming to get 60fps @ 1080p, 670/7970 now and upgrade when it gets long in the tooth is the best way to go.
I feel like the person who *needs* the 680 is the type of person who isn't posting for advice on a build, but maybe just notifying of their recent purchase of two 680s and waterblocks.