We’ve been (slowly) moving our applications over to Ruby 1.9.2 and Rails 3 over the past few months; we also now run Passenger 3 by default. This has been a pleasant switch for development, less so for deployment: even Phusion itself recommended running separate instances per gemset. I knew there had to a be a better way, can’t wait to try.
http://dalibornasevic.com/posts/21-rvm-and-passenger-setup-for-rails-2-and-rails-3-apps