I think you should try netbeans from netbeans.org first. It's probably the easiest and fastest way to dive into java.
You're really going to like using open source software when you get used to it. You'll never want to go back. It'll take some time though. Good luck with your new bosses.
Personally, I've used Eclipse, and I'm not all that impressed. The performance of Eclipse is horrid in my opinion, when compared to Visual Studio. The interface lags, and the load time is high. I haven't tried any other IDE's as I've heard that Eclipse is the
best for Java development, and it is what we've used at school.
I'd much rather make use of C# and Visual Studio to develop my open source software, as opposed to using Java and Visual Studio.