Hello,
I have prepared testing repository with Ruby 1.9.3 rev 33347 (i.e. bit newer version then RC1). You can enable it by downloading repo file [1] into your /etc/yum.repos.d directory. You can later install the Ruby package by issuing:
# sudo yum install ruby rubygems-1.8.10-rc1.1.fc17
Please note that installation of fully versioned rubygems is *mandatory* ATM and you have to *uninstall rubygems* package prior installing this test release to avoid version conflicts. This will be fixes as soon as final release of Ruby will be available.
Vit