So what did you end up buying? It's been a couple of months.
I have to say that I don't agree with several of the comments below, primarily because I was comparing four-seater convertibles in July 2008 and examined the BMW 650i, SL550 and (by chance at the MB dealer) the CLK63. In the end I purchased the CLK.
I live in California, so a convertible is a 'must' and after having driven the CLK63, I was in love. I'm not sure if it's still the case but at the time it was claimed to be the most powerful four-seater convertible available. It certainly lives up that title and is an absolute rocket. The handling is excellent and equipment level is pretty good (that was something that the BMW did a bit better on).
I hear the comments about the CLK being "feminine". Frankly I don't agree necessarily and it's probably irrelevant. Nonetheless, I do get a lot of compliments from women, so that can't be a bad thing
I have never enjoyed a car more (and I modestly collect cars).
Just my 2 cents.