So this is interesting. After getting development stabilized and setting the app into production mode, this was the one of only 3 crashes that I saw yesterday:

production.log:

ActionController::RoutingError (No route for path: "robots.txt"):
    /usr/lib/ruby/gems/1.8/gems/actionpack-1.8.1/lib/action_controller/routing.rb:291:in `recognize!'
    /usr/lib/ruby/gems/1.8/gems/rails-0.12.1/lib/dispatcher.rb:32:in `dispatch'
    dispatch.fcgi:20
    dispatch.fcgi:18:in `each_cgi'
    /usr/lib/ruby/1.8/fcgi.rb:597:in `each'
    /usr/lib/ruby/1.8/fcgi.rb:597:in `each_cgi'
    dispatch.fcgi:18

fastcgi.crash.log:

[Fri Jul 01 23:08:54 PDT 2005] Dispatcher failed to catch: exit (SystemExit)
  /usr/lib/ruby/1.8/fcgi.rb:10:in `exit'
  /usr/lib/ruby/1.8/fcgi.rb:10
  /usr/lib/ruby/1.8/fcgi.rb:10:in `call'
  /usr/lib/ruby/1.8/fcgi.rb:597:in `each'
  /usr/lib/ruby/1.8/fcgi.rb:597:in `each_cgi'
  dispatch.fcgi:18
FCGI process 12490 killed by this error

At least that ought to be easy to fix. :) But you can see how any little item can cause fastcgi to flail. As you get all this stuff ironed out, it seems to run pretty nicely though.