I just got a 722. When I was researching the unit before choosing, I asked specifically about using the 722 as a DVR for OTA HD signals, without buying any Dish HD programming. They said I could do that, but there would be a $6/month "enabling fee". Basically, their $20/month HD fee drops to $6 per month: For that price you get no HD programming from Dish, but your 722 will still function as an HD DVR for OTA signals. Note that if you do things this way, your only have one HD tuner available for recording, so no simultaneous recording of different HD shows. You still have to commit to some SD programming package for 18 months however - if you're renting their 722. It can be the cheapest one (the Family package).
[edit]If you do the above $6 enabling fee only, and don't purchase your locals from Dish, you can still record them on the 722 DVR, but your won't have the program guide info. The guide info comes to you only after you purchase the locals.[/edit]
I don't know all the Dish receiver model numbers you mentioned. I assume they're all DVR's with an ATSC tuner. If any of them are just plain receivers, why would you want that for just OTA? A non-DVR receiver-only would gain you nothing if you were only feeding it with your OTA signal - just send that signal straight to your TV instead. Unless your TV doesn't have an ATSC tuner (and your Dish receiver does).