Just a little FYI for those who don't yet own a Hi-Def TV:
We have Comcast(formerly Warner) and when we added the digital DVRs to each room, we were able to receive the HD signal on the current non-HD sets at a vastly improved resolution.
While it's not a Hi-Def quality picture, it's digital(DTV) so it's comparable to watching a standard DVD disc movie.
This was great for us since we only have one HD television but a couple of decent old-school large projection TVs. The pic is reformatted so you won't be using all the screen available but it's worth the trade off.
The analog signal is now almost un-watchable compared to it's digital counterpart.