Have mine on order - can someone let me know if there is anything special I should know as to accessories

 

Go for the illuminated door sills.

What are the options and specs that you ordered?

 

Be prepared to be VERY happy. The engine in fantastic. There is so much power that you can have a lot of fun during the break in period. The paddle shifters are a really nice addition. I had a blast with them blasting my way through some winding switch roads. Amazingly, the mileage is very good. I averaged 27 at 90 on a 850 mile trip last week. The engine snoozes at 2.2K rpm at 90 but there is plenty of torque to push without resorting to kick down. The MB service advisor (just brought it back for post break-in service) said that the car seems to get better mileage at speed.

 

I get better gas mileage when I go fast too...

17mpg at 70mph!

 

I just drove one the other day and was seriously impressed, the power was very very strong and the exhaust sounds tremendous.
The paddles were perfect and the steering wheel was quite a bit thicker and richer than the wheel in my E55.
The CLK550 is an absolute performance bargain!