I do most of my Ruby development in TextMate and Java development in IntelliJ, but both have quirks with JRuby. I’ve been checking out Netbeans 6 M10 and the Netbeans Ruby IDE. There are some nice features and great JRuby support.
I was having a problem tracking down a bug in my JRuby code. I fired up Netbeans, set a break point and stepped though the code. It worked great, I found the problem immediately.