I agree that the .each method may not be the best looping construct to teach first and I agree that some people do get a bit over zealous about which constructs you 'should' be using.

I feel it's definitely a good idea to ensure the reader is introduced to the .each early though. I guess it's taken for granted now as lots of languages have added their own versions of them, however for myself, coming from a language that doesn't have blocks it's a really good way to start to understand how they work.