New they go for 60k! So yes, 50k would be about right. I'm guessing you got it for 40k.
And no, they shouldn't be cowly from 60 on up! I have driven the CLK at speeds of 100 mph plus and was actually amazingly suprised that it handled so well! I didn't think it would. Great car though!
BTW, if you got heated seats and rain sensing wipers, then I'm thinking you should also have XENON. Ours has the pkg of all 3... winter pkg I believe.