I have only owned this car for 5 months and love it. Previous car was a 1998 Porsche 911, while the Z4 cannot compare to the 911 in performance it comes very close and cost a lot less in purchase price and maint. cost. I also think it is a better looking car. I have gotten more looks and compliments then I did with the 911.
Looks, comfort, performance, reasonable gas mileage 25 mpg avg. and ergonomics
I think the z4 should come standard with 255hp, it would then be much closer to the Nissan 370Z and the 911