sure... but ruby is on a yearly release cycle and i don't know about you but this does get me pretty excited. brings out the fan boy in me ;-)
also it gives me heads up that hey new release of ruby coming out soon, maybe i should go test the gems i maintain and make sure they're going to be compatible. RC2 is pretty close to p0
It seems like it'd be possible to automate gem testing for this scenario. Take the 1000 most popular gems, run the tests that come with the gem in 1.9.3. Run the tests again with the RC and see if any that succeed with the stable version fail with the RC.
Many Rubyists use Travis to do CI with their gems, and have ruby-head testing, often with allow-failures set. Here's one of mine: https://travis-ci.org/drapergem/draper
also it gives me heads up that hey new release of ruby coming out soon, maybe i should go test the gems i maintain and make sure they're going to be compatible. RC2 is pretty close to p0