I have 3 TVs connected right now. One 722 ( duodvr ) in the family room ( main TV ) and another 722 in the master bedroom. I have the SD output "backfeed" to the loft from the master bedroom. I used to have the family room connected to a TV in the attic, but we tossed the tv out and never replaced it. You can watch all of the channels on the SD feed, it is just not an HD output. I normally watch "HD" channels on the SD output when I am in the loft because they look slightly better to me. You can even switch to letterbox if you want the whole screen (with bars). We normally watch everything from recordings so "live" isn't so much of an issue.
There is a "whole house" DVR on the horizon, but I have not seen any potential dates on that. There is a sticky thread about it on this site. ( xip )