The Rails Way

The first paragraph of page 4 reads: "The first thing it does is to check for the existence of vendor/rails in your project, which would mean that you're running edge".

This is not necesserarily the case, you can just freeze gems there with the task rails:freeze:gems. That's an important feature. For example it allows a single development machine to have a tree of projects where each one may run on different Rails versions. And you are confident they won't interfere with each other. That's my own laptop after a couple of years of Rails development.

You have the same independence and confidence in production, in case you host several applications in the same machine.