The 722K with an OTA module can record 4 things (2 Sat/2 OTA). I use that throughout the Fall/Spring TV Schedule. I have openly stated many times that I think the 722K is the best DVR Dish has ever released. That box with a Google TV enabled Television would make for a great setup.
Many folks don't know this, but even though you can add OTA to Directv via the AM21, it doesn't increase your available tuners for recording. You can still only do 2 programs. That is very limiting to me.
Personally, I think a 4 Tuner DVR (4 Satellite tuners) would be the perfect base for a true whole home DVR. One 4 Tuner box to record and then every other TV could have a box for Live and viewing of DVR material (plus the ability to add timers to the 4 tuner box). Better yet, Dish could write an app for all of these TV's & Boxes (Google, Vizio, Roku, etc..) that gave them access to the 4 Tuner DVR box. Eventually.