Not so fast...
Judging by Tivo sales this Holiday season I wouldn't count them out so fast. We're on a voom forum for which it's all about HD and as things may be moving that way, it's still moving slow. Plus, Tivo is moving that way also with the Cablecard.
I currently have a Tivo and the SA 8000HD DVR from Comcast. I would gladly pay 10 dollars per month for the cablecard plus the $299 for the lifetime service from Tivo for a HD Tivo.
The SA records HD and has dual tuners. That's as much credit as I'll give it. It's ugly, clunky, and you can't start a show which is in the middle of recording without rewinding to the beginning and then getting tossed from the show when it finishes recording.
The Tivo has a reliable guide, smart season pass feature which let's you give priority to recordings, wishlist recordings by actor, title, keyword, and more, can stream mp3s and jpeg files from my computer, can transfer shows to my laptop for business travel, and it's all done in an intuitive, fluid and speedy manner so that my grandmother in a nursing home can even use it. If a person has multiple tivos they can even transfer shows between rooms. There is a reason the people that own them are so evangelical, just try using one for a while.