Btw, I bought a ReplyTV more recently, and the Tivo is much better.
Other things I like better... the "fast forward" over the commercial skip. The commercial skip in the Replay isn't all that good (and often skips part of the actual show), and using the 30s skip is also difficult. The fast forward on the replay isn't as good as the Tivo's, and besides, the fast forward allows you to see the commercials that might be interesting (and skip the ones you've seen constantly or just suck almost as fast as the 30s skip). I've really come to love the "green progress bar" on the Tivo, to let you know where you are in the show (and its somewhat sick to be able to tell exactly when a commercial is going to come on when they schedule them always at the same time in a show). I really like the guide on the Tivo, even though its not in the standard block layout (other Tivos do have the block layout, and I don't think its as good). And you can actually remove channels from the guide that you never watch, as opposed to the stupid Comcast digital cable box. The built-in tuner of the Replay is nice, so you can still channel surf on it, you can't really channel surf on the non-DirectTV Tivos. Of course, you can't really channel surf on the Comcast digital cable box either since its so slow to switch channels (especially the digital ones).
And when I'm somewhere else, say in a hotel room on vacation, and I'm without a Tivo... it sucks. You can't just pause or rewind the TV. And when I'm listening to the radio in the car, I wish I could rewind what I'm listening to if I miss something. Everything should work like a Tivo.