When using jruby use Nail Gun!

Nailgun is now included in jruby at least it was in 1.7.3.  It's badass.  Basically you start up a jvm server via

jruby --ng-server

it's a good idea to have the server call load up all your jars in the classpath, this works well

jruby --ng-server -J-cp "<folder>/*"

you have to use the quotes and the * not *.jar either

then just startup your jruby via

jruby --ng 

viola your load time is cut in half, maybe more