I have an E90 M3 and a new Cayman R. When I get out of my Cayman and in to the M, I feel like I'm driving a sloppy cadillac. I used to think the M was so efficient, smooth and controlled. Then I drove a Porsche. They are the next level of smooth and controlled; however, it does take a little seat time truly appreciate the differences. The M is still the ultimate all around car for DD and track work, but I'm not limited to that right now. So I am lucky enough to DD the M and use the Cayman on the track.
On a side note, don't be so quick to discount the power of the Cayman. I used to do that too. I always thought it was too weak for the price you pay, but this car has some hefty power curves and the weight is 700-900 lbs lighter than an M. Even though the peak power isn't as high as a Corvette or Mustang, the power under the curve is quite strong. This may explain why it's actually just as fast to 60 as the M is. Since I have both, I can compare the two quite well and I think the acceleration probably goes to my R just by a little bit. But then again, my M is loaded with all of the heavy options. All it took was a random Saturday test drive in a Spyder to change my mind about the power and ultimately get me to consider the Cayman for a track car.