If you look back to SDTV days, I can't find a DVR built into any model for years. Let's say there are none.
-> Why not an external DVR? Also, remember that HD content is tightly under control so you may discover it's only available if there is no DRM (see MPAA, DRM, RIAA, and more on google.)
Also look closely at the DVRs that do record HD. You find that most of the time, the recorded content is stepped down to 480p or 720.
Bob
Are there lcd or plasmas with dvr built in? I do not want to buy a tivo, then have to have a subscription.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic