According to a short post by Charlie Demerjian over at SemiAccurate, the GeForce GTX 580 is enjoying much better yields than the GTX 480 ever did (reading between the lines). The latter, if you recall, was plagued by dreadful yields, and therefore very high manufacturing costs. The fact that the 580 is much better in this respect is very good news, because it means NVIDIA and AMD will be able to engage in a price war, should the competitive situation call for it. And I love a good price war.
Besides, when Charlie says something positive about NVIDIA, you can bet that it's true.
He also mentions a GTX 560, which should make the $200 space very, very interesting. It's going to be a good winter if you're looking for a new high-end graphics card.