The problem will be getting the channel list / channel numbers to match up with a lineup from some provider. If you aren't going to do that it's kind of a waste of a Tivo.
I am a HUGE Tivo fan (I own 4 and will probably own two more by the end of the year) but the features that differentiate Tivo from other DVRs are useless for an FTA application. You'd probably be better served by a DVD burner with a integrated hard drive.