The latest cudaminer update really boosted some khash. I've been testing around with a few cards and a gtx760 went from 150khash to 200khash, which is a decent increase. This is still not close to being as effective as amd cards but its progress. A comparable card of a similar price of amd will probably yield 500khash or so. Currently running two 7950's which gives between 1100-1300khash, but its not too stable past that. I think anyone who wants to be a little more serious about mining should switch cards to amd. You can always sell them at the end, assuming you dont fry them