I just had the HR21-700 DVR installed by Directv for free.  Total out of pocket for me to upgrade all my DirecTV standard equipment to HD was $19.80, not counting the cost of the HD TV.  This is a really good DVR/DirectTV receiver.  The HD channels are awesome.  I watched the Colts/Tenn game last night and didn't see any blurring.  I watched the Leafs and NY play the other night and I was amazed at how easy it was to follow the puck.  Really had trouble with that with standard tv.

 The Guide is definitely different than Tivo's format.  I am still trying to figure out how to setup a Favorites channel list.  The DVR functions pretty much the same way with some minor differences.  Program search is almost identical to Tivo.  One function that I will dearly miss is the two tuner record buffer I had with my DirecTivo DVR.  I can no longer pause a program on one channel and watch another channel.

The remote is a definite upgrade on the DirecTivo remote.  It is very ergonomically designed.  All the important buttons are easily reached with the index finger, (or thumb for you knuckle draggers, lol) as you hold the remote. 

Overall, I am very satisfied so far.  I have not experienced any of the lock ups that reportedly occured with the HR20-700 or earlier models.

I'm in the same boat. I have decided to switch to FIOS-TV and the THX Series 3 DVR once my contract with DTV is over this December. They are forcing me to choose between them and Tivo, and Tivo is going to win that battle every time for me. I tried DTV's "DVR" and despite their customer service people telling me it's the "same thing as Tivo", it is no more a Tivo than a Hyundai is an Aston Martin.