One of the things we always notice when we watch people play OB is that they forget they have more than just one finger. Not only are you encouraged to tap away with more than just one digit, OB was actually designed with that in mind.
Many of the projectile patterns like multiple meteors on screen at once can be much better handled when you attack them with at least two fingers, one for each meteor for instance. This is particularly useful on the iPad where you have more room to use all your fingers. You can actually use up to five at a time.