I'm frequently suprised by how many people are only aware of one zoom method or the other. Even back when the iPhone was released, I remember a couple of reviews lamenting the lack of arbitrary zoom for the times when the double-tap auto-zoom didn't get close enough, and some others complaining about having to mainly zoom and asking for something automatic. It's as if knowledge of one feature makes you less likley to be aware of the other.

Reminds me of the idea I've hear taught in programming: give users only one way to do something, and you dissappoint some people, but give them more than one way and you'll confuse everyone.