From the rough performance estimates out right now (mostly just of 3dmark), I'd say G80 looks to offer impressive performance, and with matured drivers, it can still yet increase. Personally, though, I'm much more partial to actual gaming scores, which are a much better indicator of performance.
But what I'm more interested in right now is everything else; aka the architecture, but more importantly, as a gamer, the new AA engine, what new overhaul did AF filtering get (that was much needed!), and what kind of IQ and extra features we'll be looking at. Performance is just a number (yes, a very important one), but I want to know all the big changes. That's something a mere 3dmark score really can't convey.