I have a 722k - no experience with the Hopper, but can offer
these observations:
"Free" is a relative term. DISH may waive the upgrade and
installation fees, but the Hopper DVR service will cost $10
per month vs $6 for the 722k. I think each Joey will cast
$7 per month. DISH will probably require a new two year
commitment if you upgrade - not a big deal for satisfied
DISH customers who don't plan on leaving.
If you live in a DMA without DISH local channels in HD (as I
do) the Hopper's ability to record all network prime time
programming may be of little value. We get most of our
network programming OTA in HD. I have to turn the antenna
to get FOX, so recording often comes down to a choice: ABC,
CBS & NBC in one direction, or FOX in another. The three
usually win so our FOX shows are mostly in poor quality DISH
SD. (Oklahoma - West Virginia game last night was a mushy
blur.) Until last week, the Hopper didn't have OTA
capability. Now there is a single channel USB OTA module
available. Two OTA channels vs one - the 722k wins.
Best I can tell, the Hopper requires a subscription to
AT120 or higher. I have Dish America and don't plan on
going higher.
Lack of DISH local channels in HD in my DMA plus the
Hopper's higher equipment and programming cost will keep me
from "upgrading".