There were problems with the earlier 7900GTX's. The "reloaded" ones were supposed to fix that. But really they have moved focus onto the new generation. The 8800's are far superior in performance and image quality, and they smoke the 7900GTX in current DX9 titles. So as far as 7900's look toward the cheaper $150-200 options along with the X1900GT and X1950 pro. If you want the best DX9 performance, get an 8800GTS or GTX. If you want the best inbetween, grab a X1950XT for $250-300 as it offers 7900GTX performance for less money.
Anyway, We have no idea how well the 8800's will do in DX10, but we do know that they are smoking the last generation cards in DX9.