I just upgraded one of my 622's to a 722. I requested self install at the time of ordering and they shipped it straight to me. I received the 722 two days ago and the swap out went fine. Dish included a return UPS label to package the old receiver in the same box and ship it back.
I would have upgraded both of my 622's, but I own the remaining 622. When I had the system installed in May 2006, Dish would only lease one 622 and I had to buy the other. I am sure this had something to do with the 622 was a new release and they were limiting access.
Anyhoot....love the 722 and it is working just fine.