it's good but not that good, gets extremely repetitive.. same with fruit ninja and jetpack joyride.. all deleted from my device
i think of it as good mental exercise. going for a jog gets repetitive, but it's quick, easy and gets the job done. Sometimes I just want to force some quick reactions, I find it great.
I find it and polara compliment each other, polara is side scroll 2d, and each section you have to perfect then move on, you pass a checkpoint before each hard part so dying doesn't really matter. totally opposite of never knowing what's around the next bend. I'm usually in the mood for one or the other.