Check out my 3-part YouTube presentation on my Debian Stable Vagrant box at
http://www.youtube.com/playlist?list=PLfd4iay29eVBey-eRCvjWvO1pGj4_E_Us . Your Ruby on Rails environment will be ready to roll in MINUTES instead of hours. If RVM behaves in unexpected ways, or if you need to make sure that your Gemfile, gemspec, setup scripts, and setup instructions are complete, it only takes one command and a few minutes to return to the original Ruby on Rails setup.
Because my Vagrant box is based on Debian Stable instead of Ubuntu, maintenance needs are very modest. This means you can spend more time working on your projects instead of waiting for long updates to finish.