It probably could be considered a failure because it couldn't nearly match up to the success the GF4TI is/was. And yes the DX9 performance isn't the best. 6800GT sells well to ethusiasts, and once they get the more affordable 6600's it could be considered the biggest win for Nvidia yet. But we'll have to wait and see. The Radeon 9800 remains king in many people's minds, and managed to cross over into OEM builders (something Nvidia held the crown for years). Actually the FX5200 is a mild win if you consider how many cheapo OEM computers have those.
From a personal stand point, I really very happy with my FX5900XT. I upgrade from a TI4400 and I did see an improvement in performance. Admitedly the AA/AF isn't as good as R9800 and the DX9 makes me
but other than that a very solid piece of hardware. I plan to keep this beauty as long as I possibly can