I got a 6800 card to, and dissapointed like most of ya about this issue, its a bad thing that Nvidia have done here, and i just turned from ATI.
I tried to install the nvidia dvd codec thing, it works like beeeeep, they write it work when usin WMP 9 or later ´(i have version 10), but the codec dont show up in the process line as nvidi claims, i then found out that it consisted of a mediaplayer, hmm, then tried that, it did work, well at least a bit better, but still a bit stuttering in the video, but the audio wsa even worse than before, on the possitive side, i can now play all files through this player in fullscreen without corruption like i have with all other players :-(
What can i say? well i can´t send the card back, but unless there is a driver soon, then i will spread the word, thats all i can do, but if plenty of people do it, then Nvidia will be in trouble.