It is worth it because when Tivo's license deal runs out in a few years they'll have the replay patents to fall back on which were settled out of court between the two companies many years ago. So essentially this allows DirecTV to tell Tivo to screw off.
After a 97 million judgment against Echostar having the replay patents is a huge boost even if they never add a single feature set. Naturally they probably will add some features, make things look a bit nicer etc... but to say its worthless is short sighted and incorrect.
That USB device is just a rebranded device from another company (just like ReplayTV PC); it is not a ReplayTV/DNNA made device. They are after ReplayTV's patents. We may see a feature or two, but as said above; if its not the true commercial advance, unfettered networkability and the use of DVArchive, then who cares, all DVRS after that are 99% the same.
I have two Replay TV boxes, one has Commercial Advance the other doesn't but if you use the right navigation arrow button it does skip the commercials, sometimes it goes to far, or not enough but most of the time it works OK. I have used Tivo and Replay is by far the better unit, bad marketing and a bad name did not help their sales, ever heard of anyone saying they were going to Replay TV a program. Tivo is a catchy name and easy to say.