Pick your poison - which IDE do you prefer? Have you tried Netbeans recently, because the NetBeans-team recently re-vamped the GUI completely. The NetBeans team have also gone completely Ruby-nuts in the latest 6.1 release and NetBeans now has Rails 2.0 support out-of-the-box.
Sun even went a step further and hired two of the main Jython developers (Ted Leung and Frank Wierzbicki), in order to get Jython and eventually Python support into NetBeans.
But check out the in-depth review at JavaWorld.
