Right now, Series 1 and Series 2 DirecTivos have the same software features.

However, Home Media Option (HMO) is available on the Series 2 Stand Alone units. Tivo hasn't made arrangement with DirecTV yet to bill HMO to DirecTivo owners, so it's not available yet but probably will be in the future (my opinion).

Other than that possibility, both Series 1 and 2 have dual tuners. The USB in Series 2 could also be used to stream shows to other Tivos in the house in the future as well. I am hoarding Series 1 DirecTivos because of the ripping ability. I have 3 now. Need more.