I've had my C63 for a few months now and it took me a while to like it properly.
Initially i liked it but for some reason i still prefered my 335d and even considered getting rid of the C63 for an M3.
Now though after we've spent more time together, i absolutely love her now
Its probably been helped by some drier weather recently and now realise fully how different a turbo diesel is than a N/A petrol engine.
Looks wise, the BMW still just edges it for me and the C63 is a grower for looks.
What a car does around a track isn't really of interest to me - its how they perform on the road as thats what i use them for.