I sold my C63 507 estate a few weeks ago due to the milage and the fact it was out of warranty. Absolutely loved it. The engine is a masterpiece and once the exhaust has been fettled sounds outrageous. The gearbox on the other hand was slow and sluggish and constantly annoyed me.
The M2 that has replaced it puts just as big a smile on my face but for different reasons. Not so much the noise and drama but the driving feel and chuckability. Both are great cars so you can't really go wrong.
P.S Ignore Bieber as best you can.