I have a co-worker with one of these TW-PVRs. He loves it. Its worlds better than live tv, and it has the capability to record 2 things at once!

BUT - it has some big down sides. It is very immature UI and feature set compared to TIVO or REPLAYTV. An example - There is no way to see how much free space there is and it will just stops recording when it runs out (no warning when you setup the record or when it tried to record). You might sit down to watch your fav show and only get 10 minutes!

It still beats live TV!