It’s hard to keep your project stable while still messing around with Rails 4.0. But switching between multiple Rails versions (3.2.12, 3.2.13.rc2, 4.0) became a breeze after reading Daniel Kehoe’s excellent Updating Rails.

Big Caveat

A lot of people have used Engine Yard’s RailsInstaller. Don’t use it. Although it’s great to get up and running right away, it’ll bite you hard in the ass in the future. It actually installs RVM at the system level (for all users, not in your usr directory) so your carefully tweaked configs won’t match when switching between project directories.

Fortunately, Rachel Ober has a great article on how to Uninstall OSX RailsInstaller.