The CLK500 cabrio is a fantastic car. No compromises with this car--it doesn't even really need four doors because you can drop to top with the keyfob so backseat passengers can comfortably enter standing up. I use it to get my kids and their carseats in more easily than seating them in our SUV. Performance is fantastic. 0-60 in under 6. I've done 135 in it and there's litterally no difference in handling between that and 65. Braking is astonishingly short. Great car for family guys who want a sports car or tall people--drivers up to 6'7". One warning though: The real mileage you'll get in this car is about 16.5 mpg.
The automatic top can be opened or closed with the keyfob, which makes it far more useful than a regular convertible. You'll drive with the top down a lot more often.
There's nothing to improve about this car except the gas mileage, which is probably impossible considering its performance.