> I really wish people would make virtual machine images with dev environments already set up on them

I think this is actually often more of a problem in the long run, as it just pushes the learning of how RoR interfaces with the rest of the stack to later. If you're seeking to teach someone how logic, program control flow, and separation of concerns work (as the author did by abstracting the "grunge work" as he calls it), why not pick an environment a bit more bare-bones?

I see the merit in allowing someone to get something up and running rapidly, but I think they may miss important concepts when learning in an environment that favors convention over configuration.

Because the author explicitly wanted "not to waste his time on banal unrelated issues" except those directly related to the project at hand.

He's not missing important concepts but deferring important concepts to learn other important concepts that lead to progress today.

You end up paying back that deficit one step and one layer of abstraction at a time:

    Some of Brian's biggest forward mental leaps came when he took 
    a step back away from the day-to-day project grind, learned new 
    concepts in a course or from a book, and then thought about how to 
    apply them to SwearBuy.

It really depends entirely on what your goal is.

If your goal is to tinker with a new language, or a new tool, it would be really nice to start from a working example that you can fiddle with, rather than being stuck with the sometimes arduous task of configuration.

They did just that in the coursera course "Software Engineering for Software as a Service". A VM is available for download and as a rank amateur I found it a great way to dive in. https://www.coursera.org/saas/