Have owned for 2 yrs now and I still love it. Gas mileage has settled down ~15mpg. I took it in for a checkup ~16k mls; got a 328 loaner. Wow, there is a massive difference. I am completely and forever spoiled by my M. Had to buy new rear tires after 1yr/10k mls=$850. My fault-too much M button w/ traction control off. My only dislike; it is too much car for my streets. Almost unusably fast- no chance to really see what she can do!
Steering/feedback/suspension and responsiveness. Wonder what the new M5 will be like. Still glad I bought it - depression/recession and all!
It's a little heavy - and you can feel it while breaking and cornering. Not bad, but you definitely know that it's a sedan. Ventilated seats need a little more oomph...it gets hot and unless I'm perspiring (not in the M-that's why I have a beater too!) - it doesn't work that well.