In each case (with ReplayTv, Ultimate Tv, and TIVO) there are minute differences between the recording units and the services you receive. I think TIVO is easiest to use but sadly doesn't allow you to fast-forward through programs fast enough. Ultimate TV, on the other hand, has an astonishing 300X fast-forward and 30-second jump features that TIVO lacks. However, even with the latest software upgrade (which these machines do automatically, by the way) it is far more difficult to search for programs using the Ultimate TV technology compared to the two other systems. The first Replay TV units also had the 30-second advance and their program searching technology was perhaps the most "intuitive" but you could only record a few programs on those early systems.