I've had my 2004 JCW S for all of it's 94,000 miles and it's a great car. Fun to drive, economical and reliable. Mileage back and forth to work in mixed highway and street driving is 28 mpg. Highway mileage for me is 34 mpg.
I'm not a huge fan of the latest model; they are more isolated feeling. That said, we added a base Cooper for my daughter earlier this year. So, yeah, they're good!