Well the most powerful cards always have the highest price tag...and it looks like ATI might get that with the 3800 series. In that case people that want the fastest will pay, and in theory their midrange 'might' be around the same performance and cost as the 8800GT, but with new specs like dx10.1.
So there may be a quite a few reasons to go ATI in a few weeks. And the fact that Nvidia just released a card that is so fast and so cheap actually makes me think they are worried about ATI's release. Think about it...why else would they release such a cheap card that comes so close to the GTX??