Most of the satellites have some 8PSK on them. I think the only ones that do not are the 77 slot since 8PSK requires more signal strength and this bird is not at its designed location.
That's about it... more bandwidth. Less hacked FTA receivers can tune 8PSK without special boards. But they've sewn up the pirate groups pretty well with the card swap.
Almost all of the HD on DishNetwork's system is already in 8PSK already, since all HD receivers can do 8PSK. The only HD you'll find in QPSK mode is on 77 and 118.7.
The puzzle begins... remember there are 3 HD installation types. 110/119/129, 61/72/77, and 110/119/61.5. The last one is the real kicker that puts a kink into things. If you add HD to 72 you have to add it to 110/119. There is room on 119, so possibly you'll see something once they get things situated on the 72 slot.
There's always DirecTV with the loads of new national HD they've been adding
(in a sarcastic tone)