Neutrino: Yes, only one 722. It supports two rooms though, so that's good enough for my use. I don't need two separate 722 units in my house, just one 722 split to two rooms and a normal Dish receiver (no DVR necessary) for a third room upstairs.

Dylan: I spent a lot of time fishing through the threads on DBStalk for peoples' opinions, but the most objective side-by-side comparison I found is here:
http://www.dbstalk.com/showthread.php?t=95242&highlight=vip722+vs+hr20
Look at the PDF file in that thread for a comparison of the various features. There are some where HR20 comes out ahead but the heavy hitters for me seem to all favor Dish. There are, of course, going to be subjective qualities that don't come out until I've actually used them myself, but based on the checklist of features available, I gotta go with the 722.

Dish's service also comes out about $10 cheaper for my particular needs. Coupled with the $199 for HR20 vs $0 for 722 fees, it was pretty much a no-brainer. And, my folks have Dish Network, so I can save them $50 with the referral program. Everybody wins.