While we love this simplicity, it depends on a system install of Rubygems. To get this experience on widely varying development environments, we created the Heroku Toolbelt, a one-click installer for every major platform.
Going forward we will be sunsetting support for the heroku gem in favor of the Toolbelt. If you're already using the Toolbelt, you're fine to stop reading now. To verify whether you're using the gem or Toolbelt, use heroku version:
$ heroku version
heroku-toolbelt/2.32.11 (universal-darwin12.0) ruby/1.9.3 autoupdate
If the output includes heroku-toolbelt, you're all set.
