I just got my sammy plasma and absolutely love it. I have Cox HD cable hooked up via HDMI to my Onkyo TX SR706 AVR. I have my ONKYO HDMI video output set to Through. When viewing HBO HD why does my screen say 1080i?, I thought HD signal from cable box came as 1080p
Also when playing PS3 (Call of Duty) it says 1080i as well, it says on the back of the game it supports full 1080p.
I think the only time it goes to 1080p is when I play a BD movie.
I can force my AVR to display 1080p instead of through, but am I compromising picture.

Thanks

All HD cable is broadcast in either 720p or 1080i as far as I'm aware.

Call of Duty should be playing in 720p. That's what it's native resolution is. Do you have 720p checked as an option on your PS3? If not, your PS3 is doing unnecessary upconverting.