I am sure this is not news to the pros, but I have been using some great tools provided by Postmodern to make my Ruby on Rails development life easier on OS X. Rather than get caught up in the RVM vs RBENV + ruby-build battle, Postmodern slipped in under the radar and provided some great alternatives to both.
- chruby to deal with switching Ruby versions
- ruby-install to install Rubies
- chgems if you miss RVM gemsets and want something else to eliminate the need for bundle exec
Mac OS X users can install chruby and ruby-install through Homebrew or you can always use terminal. These tools are lightweight, well maintained and you can even find Postmodern on IRC to help with any questions.