Netflix is also popular because it's $8 a month.
The general consensus seems to be that the DirecTV dvr is head and shoulders better than Comcast's but it has fast-forward/rewind gayness as well. Once in a while if you hit the "skip ahead 30 seconds" button too many times quickly it jumps all the way to the end of the recording. This is particularly infuriating when you were looking forward to watching a football game and the final score is on the screen at the end of the recording. Also, if you pause it and then hit the fast forward button, it advances one frame per button press, but if you press rewind, it may go back one frame, or it may go back 2 minutes, or forward two minutes, or some other totally fucking random thing. It doesn't seem that difficult to manage fast forward and rewind, but DVR makers fail at it.
It works flawlessly in Windows Media Center, but since there are no cablecards for DirecTV that isn't a great solution either.