Playing on my MBPr.
1440x900
details on high
things light shadows, lighting, ambient, foliage etc on low
looks and runs better than it does in bootcamp
in bootcamp I can't do 1440x900 and the game doesn't look good unless I do at least 1680x1050
overall, very pleased
EDIT:
reset the nvram and smc and I can play nearly maxed (except shadows and other resource hogs) without terrible slowdowns. I can't see my fps but it's pretty smooth. The UI (items menu) is slow as all hell, though.
No clue how a GT650m compares to a 4850, though.. you should at the very least be able to play it.