As I said, even if it had been released with the same features as the iPad/iPhone/Webapp/etc., it would have been functional enough to try to persuade the family that it was acceptable. Using a different device to set up scheduling (past 24 hours and not limited to just the LiveTV grid) or not having any kind of sorting of recordings, or no listings of shows/movies, etc. for the ATV app just doesn't cut it as usable. Possibly I could deal with it myself, but not for family.
Is this question really just a way to beat up on Tablo? Tablo is fine for what it does, it's just lacking in features. Check the Feature Requests forum and you'll find a lot that Tablo lacks and consumers want.
But to answer your question, the list can get large, but a few are:
Ability to add extra time (up to 6 hrs) to any recording AND/OR start recording early.
OnePass (schedule by keyword or set up season passes, etc).
Keep X number of recordings.
TV preview in corner while browsing guide OR small guide overlay while watching TV.
Instant channel changes.
Record from the buffer.
Suffice to say, the TiVo meets our needs. I was just tired of paying a monthly guide fee and I also wanted a one device solution so I wouldn't have to switch inputs between the AppleTV and the Tivo. I decided to give the Tablo a shot when they announced they would have an AppleTV app. The current state of that app does not suffice and I decided not to wait any longer for Tablo.