Consistency is important when designing interaction with user interfaces. Consistency makes it possible to re-use what you learned in one application in another. Unfortunately there are many application developers that invent their own interaction principles, even when their is an established praxis. But, it is even worse when someone who established the praxis provides an inconsistent user experience. Yes, that means you Apple.
Case in point: zooming in and out of a document:
- Safari: Apple +/-
- Keynote: Apple </>
- Preview.app: Apple +/-
- iPhoto: Alt 1/2
At first I thought that Apple +/- was for increasing and decreasing text, but in that case Preview.app is inconsistent. Oh well, moving on…