We won't do anything to handle exceptions in 3.1. For 3.1, this is definitely a "use at your own risk" feature. Besides handling exceptions, there are a bunch of caveats for using this. You need to use the right web server (unicorn or specially configured passenger), along with the right proxy (nginx or apache with special configuration) and Ruby 1.9.

I've got ideas for handling exceptions, but I just can't make it happen for 3.1. :-(