E>Rails 2.3 is finally done and out the door. This is one of the most substantial upgrades to Rails in a very long time. A brief rundown of the top hitters:
E>Templates: Allows your new skeleton Rails application to be built your way with your default stack of gems, configs, and more.
E>Engines: Share reusable application pieces complete with routes that Just Work, models, view paths, and the works.
E>Rack: Rails now runs on Rack which gives you access to all the middleware goodness.
E>Metal: Write super fast pieces of optimized logic that routes around Action Controller.
E>Nested forms: Deal with complex forms so much easier.

E>And that’s just the tip of the iceberg. We’ve put together a complete guide for the Rails 2.3 release notes with much more information. Be sure to checkout the section on what was deprecated when you’re ready to upgrade your application.

E>You install 2.3 with (the final version is marked 2.3.2):
E>

E>gem install rails 
E>

E>If you’re running on Passenger, be sure to upgrade to 2.1.2 as well. Rails 2.3 doesn’t run on older versions of Passenger!

E>We hope you’ll love it.