I'm thinking about unpacking the gems that my app uses. If my
development box has exactly the gem versions I want to unpack, do I
still need to specify each gem's version in config/environment.rb?
If the versions installed on your dev machine are what you want, you
won't need to specify the version. The gems:unpack code grabs whatever
version is loaded when it's run. The versions in vendor/gems will be
preferred regardless of what's installed on your production machine.