Instead of "bundle exec rspec spec", I think it's more user-friendly to use rspec's built-in rake SpecTask detailed here:
This is not an available-by-default Rake task (it seems to be rspec 1.3), but I admit I would prefer one because it's shorter to type.
In RSpec2, the Rake Task automatically uses bundle exec if the project uses Bundler.
Where in the guide would you introduce this?
At the point you start with this "To run the rspec command for our bundle ..." when you begin talking about executing the specs. You've already introduced the Rakefile at that point.