I like the GUI of the 922 and would rather have the sling built in then have another connection to a device. I'm not to concrened about the functionality as I don't expect to use the sling much and don't need it to drive another TV. I also feel that with softwre upgrades it will gain more funtionality.
I called and I guess they are consistant $200.00 for the upgrade of an old 501 and they are upgrading my 622 to a 722K for no charge.
I'm actually in the same boat as you - I have a 622, currently out of contract, and looking for upgrade options. I do use the TV2 feature of my 622, but I heard the 922's new software update will enable that - although I haven't heard any confirmations yet of people receiving this update, so we'll see. Although I rather have the Sling Extender - but I guess that's not happening.
So assuming 922 gets the update, here are the two options I'm looking at right now:
Option #1:
ViP 922 - $200
TOTAL: $200
Option #2:
ViP 722k - FREE
Sling Adapter - $100
Google TV - $180
TOTAL: $280
The good thing about option 1 is it would be cheaper and is only 1 box to deal with (instead of 3). As for the GUI I don't have an hands-on experience with either of them, but I'm thinking the Google TV UI would be better then the 922's.
Plus I have more confidence in Android & Google TV's developers then Dish's to make their UI's better in the future. The best thing for the 922 would be if they built-in Android/Google TV in their future software - maybe they have that planed.
As for the Sling, from what I've heard people are saying it works much better with the external Sling Adapter then the 922's built-in.
I'm still on the fence with which way I go - hoping to hear reviews of the 922's new software update first before deciding.