peter 
2010 BMW X5 M SUV 4dr SUV AWD (4.4L 8cyl Turbo 6A)
Went in for a GT - left with X5M
 I thought the GT 5 would be a nice blend of performance and function. The sales manager suggested I drive the X5M. The X5M was much more fun to drive and more functional. Surprisingly comfortable than the GT with a more supple ride. The ride is tons better than a standard X5. The M's handling rivals virtually any sport sedan. It is big and heavy and the mileage is atrocious - but expected. Don't have enough miles to judge reliability.