Since yesterday I have been using the 180.35 driver provided by Nvidia and the previously reported MythTV patches for the current 0.21 version. I must say, the picture quality and the deinterlacer are fantastic. I am watching HDTV at 720p using about 10% of my Core2Duo 1.2 Ghz system. This is amazing, as the new driver accelerates nearly every common format (mpeg1, mpeg2, h264, vc-1).
Edit: shortly after Nvidia released 180.37 witch fixes a few bugs. Just as good at VDPAU as the 180.35 driver.