The Cayman S is a very nice car. I needed 4 seats so it was never an option. Although the back seats of my 911 a pretty small my girlfriends kids, (6 and 10 yr olds), fit fine.
I really like the cornering capability of this car and have to say it is a little more maneuverable than the M3 and is greatly in part to using sport mode. Sport mode tightens the suspension and is an active mode. The breaking is breathtaking but simply because it has the PCCB. (Composite brakes. This is an $8,000 option) Big tires also. The rears are 305's and the fronts 235's on 19 inch rims.