ruby 1.8.7 is required for Rails 3; so Leopard/10.5 users need to install ruby 1.8.7 manually to get started as if they didn't have ruby installed at all, I think.

Actually ruby 1.8.7 is required to install ruby 1.9.2. Rails doesn't need 1.8.7 and works fine with just ruby 1.9.2 installed.

  ruby - Ruby itself is prerequisite in order to build Ruby 1.9. It can be 1.8.

source: http://redmine.ruby-lang.org/wiki/ruby/DeveloperHowto#label-...

If you install via RVM, you don't need a system ruby or anything else installed for bootstrapping.

http://rvm.beginrescueend.com/rvm/install/

http://rvm.beginrescueend.com/deployment/system-wide/

Good point. I've been on 1.9 for so long I'd forgotten about the 1.8.7 requirement for Rails 3.