Maybe the SL63 is a bit too loud for a Mercedes, but that's what I love about it. I had this same reaction to the Cadillac XLR-V. The SL63 AMG makes a lot more sense than the XLR-V, but both cars border on alienating the core buyers of the base version of the respective cars.
The SL is my favorite large roadster for touring duties. I suppose the closest competitor to this SL63 is the BMW M6 convertible. The SL looks and feels good while the M6 convertible leaves me scratching my head. It's easy to argue that neither car warrants the enormous engine it packs, but I don't find the SL63 to be offensive in the way Marc does. If I had the coin, I'd certainly throw down the extra tens of thousands of dollars for the SL63 over an SL 600 or 550.
I was very disappointed with the race start option. Mercedes makes you run through an exaggerated set of steps to ensure you don't accidentally enter the launch control start. It's slightly more intuitive than setting the clock on a VCR, but there is no reason for more than one step. Why doesn't turning the transmission shift speed dial to RS instantly put you in the race start mode? Why do I also need to have a foot on the brake, turn ESP off, and then tap up on the right paddle shifter? There is an incredible amount of computing power in this car, so why do I have to tell each computer what to do? I'd think someone could simplify the process.