There's another thread on this that popped up around MGS4's launch.
I don't know the fps, but I'm pretty sure it's 768p native.
http://forums.gametrailers.com/showthread.php?p=11504605
It will display 720p, 1080i, and 1080p. The FPS is mostly steady, but it isn't locked in because things will get VERY smooth depending on your environment (like being in an enclosed area).