The X800 has a video processor too. I think even the Pro version does, which only the 6800 Ultra has it, so that's another thing to consider when comparing the lower cards. Once they start taking advantage of these it will be awesome. The cards could function as tv tuner/capture cards. Also, since they can take the signal and convert it on the fly, it'lle be nice to take a lower end card (say a Winfast TV2000 Expert like I have) and make it put out in HDTV. I've been wanting to make use of my component cables for my Xbox and Gamecube and if properly supported then I'll be able to run them into the card and have them convert to HDTV as well (compare buying a $500 graphics card to an over $1000 HDTV). Very cool things. In fact, I don't know that I could justify paying the price for one of these new cards without the feature. I think that both companies have thus far overlooked the importance of this feature, they should be promoting it more. I might even go as far as to say that implementing this might be the deciding factor on who "wins" this round of the graphics wars. Like me, it'll be easier for people to justify paying a steep price for a card that is not only the best graphics card but can do so much more.
Sadly, I agree that implementation of this feature is lacking and will most likely continue to be for at least a little while longer. I'd say they'll probably take time out for it after the big hoopla over the new cards is done (this would include going to PCI-E), so I'm gonna say maybe late summer, early fall. Then again who knows, and also I'm sure there's plenty of people out there who would love to make use of this feature and so maybe 3rd parties will develop something.
Just my thought on this (can you tell I've been excited about this feature since I heard it was going to be on the card(s)? I was even deadset on nVidia because it seemed as though ATi wasn't going to do the same (I thought AIW cards), but thankfully they did and so competition will likely breed innovation).