Well I've just seen the first full review for the 670 reference. I wont link to it since its a site that is not under NDA (seems they pissed off Nvidia in the past) but have gotten hold of a sample card to test.
The performance, if true, buggers belief. Very close to the 680 that it edges out the 7970 in most benches. Cant wait to see the guru review once NDA is lifted.