I purchased a 2005 C230 Kompressor sport sedan in September of 2004. When I hit about 7800 miles on the car, I had a fuel injector problem: under a hard acceleration, one of my injectors misfired or something but it left some scorching.... There was a field fix in place for that issue so I got all new injectors and stiffer valve springs (if memory serves). I now have 39,000 miles on it and have had 0 issues since.
Yes, the A service is about $200 and the B service just under $400 but you only have to have those services every 13,000 miles, so it's not really too bad. I usually have my oil changed once inbetween services and that does cost about $98, due largely to the synthetic oil.
All that said, I still love this car. I feel good driving it. It is the most 'point-and-shoot' handling car I've ever owned. I get 32+ mpg on the interstate and it pulls like a V-6 under acceleration. I really think MB is getting the quality control issues fixed on the newer cars.