The lack of tourqe is what disappointed you in the M3. The I-6 of that car needs to be kept in the upper rpm's to appreciate what that car is capable of. But I agree, off the line acceleration in everyday driving is nothing to write about.
Where did you drive the Cayman? I was told "no"
last time I took my car in for service.
But in fairness, it was the only one and in the showroom.