Great tip. I used this as a basis for a rake task to bing Ping and Google for new sitemaps. Thanks.
I have to agree that this seems like a lot of extra work. I personally use many of the great tools provided by https://github.com/postmodern including: Chruby for managing ruby, ruby-install for installing Ruby, and Chgems to manage my gems. I have multiple sites and this combination keeps everything happy despite different Rubies, Rails and gems. Chgems behaves similar to RVM gemsets but also allows you to get rid of Bundle Exec. I am on OS X 10.8.4. Also highly recommend you use Homebrew for package management.