I think this is worth pointing out. For those who wished the current iMac had a desktop GPU ie a 6970 instead of the 6970M then the new 680gtx is in fact better than the 6970
According to this chart the 680M is better than a 7970M and the 680MX is better than the 680M.
All in all, the gtx680mx looks pretty sweet. The Haswell iMac will probably have a 780mx which is when I'll upgrade.
680M specs
680MX specs
According to this chart the 680M is better than a 7970M and the 680MX is better than the 680M.
All in all, the gtx680mx looks pretty sweet. The Haswell iMac will probably have a 780mx which is when I'll upgrade.

680M specs
680MX specs