OK, I'm hooked.  After recording several HD broadcasts with my HD DVR, I can't see going back to an SD-only existence.  I admit that I long for 720p rather than my TV's limit of 1080i, and the DVR has MANY shortcomings, but I've found a few workarounds for my complaints.  For instance:

• I fast-forward at triple-arrow rather than double arrow on Tivo.  This gets me through commercials only slightly faster than Tivo.  Double-arrow is too slow.
• After ffwd, I hit the instant replay button instead of play, wihch will approximate Tivo's automatic jump back, and even though it jumps back further, my receiver takes a second or two to kick in with the optical input, so it works out.
• I'm getting used to hitting stop to get to a screen where I can do something with a recorded show.  I've grown to appreciate more and more Tivo's elegantly simple remote design where you can do everything with the 4-way cursor buttons, select, a couple of main menu buttons, ffwd, pause, and rewind.

Seeing The Mummy II in full HD goodness, I'm even starting to question the validity of trying to grow my DVD collection any more.