The one feature I wanted in the DTV PVR and has been claimed as a TiVo "patent" is the ability to flip between the tuners.
So I'm watching one show, commerical comes on. I hit pause, hit down, flip to the other tuner and surf the channels. Once I feel I'm done with that, flip back to the first tuner, and hit play.
That is what makes me the most unhappy about the HR20/21. I want that capability back as fast as possible.
