I don't care for the ASS but I only turn it off when I know my drive will have a lot of stops/traffic lights. I also play a little game with lightly "edging" the brakes to a stop - if I do so, the ASS does not activate. For example, when I leave a pay parking lot at the gym, at the exit booth I don't want ASS to come on because I know I'll be restarting in a just a couple seconds. If you sort of tap the pedal lightly, ASS does not engage.
But overall it is annoying, whatever the gas savings. I wonder how long BMW will stick with this feature...then again, they have stuck with RFTs, despite being generally disliked, and their sales have continued to be very healthy.