I'm really happy with our 2006 MCS. Power is good, and the handling is awesome. I find the ride with the 16 inch wheels to be very good, and the car is fairly quiet on the highway. As far as carrying capacity goes....I'm glad I also have a pickup truck. There's not much room!
The basic MINI Cooper S, while not inexpensive, is very well equipped. The price does climb very quickly when you start to add on the options. As for comparing the MCS to an M3S.....that would be a tough one. I'd have to drive both, back-to-back.