I've only had this car for a couple months. My local independent garage diagnosed a leaky rear seal, so the car does use some ATF. There is a bit of slippage when it's cold, and it takes a noticable amount of time to upshift when it's floored. Right now I'm just keeping an eye on the fluid level (when I first took it in it was two quarts low! In that condition it shifted very poorly.)
Greg, if the car you're looking at accelerates ok, and the trans upshifts firmly but not jerkily I'd say that it's ok. Mine has a noticable slippage and hesitation on upshifting. Best to drive a number of MB's to get a feel for how they are.