Day one driving to work on ECO mode on got me 24.4 mpg. It is a 20 mile ride mostly through the back roads with total of 17 traffic lights. My old X3 does 18.2 mpg on commute to work. It is already 30% savings on my fuel.
I am already got used to Start/Stop function and it works great. No more guilty feeling at long traffic stops. Once you have accepted the 4 cylinder engine in bmw you will also accept start/stop feature. Changes are hard to accept.