- Why it actually might be interesting to let your Ruby app run with Jruby instead of MRI: threading, Unicode, performance, memory (much better garbage collection), c extensions > Java extensions, use Java code directly from Ruby
- Warbler: packages your Rails / Ruby application into a WAR ready to deploy
- How get Ruby work on AppEngine
- Testing: local testing problematic, functional tests need to run on AppEngine directly
All in all I got the feeling that you shouldn’t run your production Rails application on AppEngine yet. There are to many caveats currently. It might be worth considering to move specific services of your application to AppEngine though. Especially those which could benefit most from the scaling advantages in the cloud.