I have not had problems running Rails 2.3 on Ruby 1.9.2.
Does your app have i18n?
No, none of the 2.3 apps I've run on 1.9.2 have i18n.
Also, we heavily share code and data between applications with symlinks. Symlink handling (especially the interpretation of ..) is different in all ruby-1.8, ruby-1.9 and jruby. Makes the whole ecosystem smell like different ghettos.