I've been a longtime user of the Tivo, and when my mother got an HDTV, I pushed her to get a PVR. In Canada, the only really workable option for her was to rent the HD-8000 HD PVR from Rogers, her cable company. No Tivo service in Canada, and she wasn't ready for a PC based PVR (And HD ones are still immature.)
Two things I learned from the process. The first was how amazed I was at how badly the HD-8000 was designed. It strikes me as a first generation unit, not something that was designed after people looked at the Tivo and the Replay. Trying to watch a show in the middle of recording it is possible, but really cumbersome. It's very easy to lose your buffer on a live program you were watcing, or to lose your place in a recorded program you were watching. Browsing shows is guide-based, requiring you to browse only a particular day at a time. I could go on.
The other remarkable thing was seeing my low-tech mother's reaction. In spite of all I tell her about the PVR, she still wants to watch TV live most of the time. As a retiree and caregiver, she's home most of the time, and while she intellectually understands what the box does, her habits are so-long set that she really doesn't "get" it.
Which may explain the poor UI on the HD-8000. They don't expect their users to get it either. They expect their users to see it as a fancy VCR, with the ability to pause live TV. (Tivo owners learn that pausing live TV is more of a gimmick feature, in that you almost never watch live TV.)
Watching the recorded HD does make me jealous, though. HD PVR choices here are limited. You can get DirecTV's HD-Tivo for $1000, or build a MythTV box for a similar amount of money. It is the need for the PVR that has stopped me from getting HDTV, which otherwise I want very much.
But my Mother doesn't remember that when called on the phone, she can pause it. Or that you should always record a show you see that you want to watch, to give you the freedom to switch from it and come back later without risk. She is happy with her old habit of switching channels when a commercial comes on, and coming back to the other show later, presumably missing some of it. She is even happy watching low def live, when PVRed hi-def is a few steps away. My mother helps me remember that all users are not like me, which is good.