I have an R171, albeit the 55.. :) It's stupidly over-powered for normal use, I'd imagine the 200 is perfectly adequate for keeping up with the traffic. With regards to a manual, they aren't popular but at least it's got a normal handbrake as opposed to the stupid foot-operated parking brake that many Mercedes are afflicted with, so no dramas on that front. Also, unpopular = cheaper, generally.

Do make sure that the roof operates properly - they can be big money to fix. Apart from that, I'm not aware of any specific issues - make sure it's been looked after and you shouldn't go far wrong.

Cheers,

Plug