The first question you might ask yourself is Why should/would I need to switch? The answer is simply you don't. It is completely up to you whether or not you want to. I've found that in my development workflow rbenv just works better. I don't have to worry about managing gemsets. Bundler takes care of all that for me already.
Install Homebrew if you don't already have it on your system. Homebrew acts as a package manager for OSX. It makes life just a little bit easier on us mac users.
ruby -e "$(curl -fsSL https://raw.github.com/mxcl/homebrew/go)"
Run the code below to make sure everything installed successfully. If it did you should get a message back saying Your system is raring to brew
Next we needed to update.
Homebrew makes it stupid simple to install rbenv.
brew install rbenv
brew install ruby-build
Next you will need to configure your terminal to load the correct path for rbenv. For my example I'm using ZSH. If you haven't checked it out yet, you should because its awesome. I had to edit my ~/.zprofile like so.
sublime ~/.zprofile export PATH="$HOME/.rbenv/bin:$PATH" eval "$(rbenv init -)"
Note: I'm using sublime as my text editor. Just substitute your editor for sublime to open up the file.
Note: If you are not using ZSH you might have to edit
Bonus: Using Rbenv
For my workflow I found Rbenv to just be a lot simpler than rvm. I hated having to manage gemsets and whatnot. I like simplicity.
rbenv install 2.0.0
Hit tab to autocomplete the ruby version so you get the latest and greatest.
Then don't forget to rehash after installing.
Sets the current directory to use that version of ruby.
rbenv local 2.0.0
Sets the default version of ruby to be 2.0.0.
rbenv global 2.0.0