Just found these two little gems while making the great migration to Ruby 1.9.3-p0. 

RBEnv and Ruby-Build

Both work hand in hand.  After a quick clone/install, I upgraded to the newest Ruby with a simple

rbenv install 1.9.3-p0

You can set your version globally with

rbenv global RUBY-VERSION

or set them in a per folder/project basis with

rbenv local RUBY-VERSION

Much easier to use and more verbose than RVM I think.