well, to make it short: there are plenty of great bmx games on iOS... but this is not one of them.
nothing more to do than (very) slightly tilting and occasional button pressing... the game pretty much does the rest (but it's enough for rushing through the levels levels with nearly perfect runs... first world took me about 5min?)
biggest concern (besides the pretty less "interaction"): performance! even there isn't exactly amounts of heavy gfx around, the game runs pretty laggy on a 4S device. maybe DEVs want to take a look on games like "earn to die", how to achieve speed & smooth performance with tons of objects on screen... sorry, no winner