they're saying april 17th, but they could change it. I read in one of the articles that the 8600 GTS is supposed to have around the same performance as a 7900 GS or better.
there hasn't been any official info....but rumor has it the 8600GTS is supposedly around $200-$250. There are charts for pricing of the other 8 series cards soon to launch but those are from a couple months back