I joined the #netbeans channel on FreeNode last week and the discussions there are really great. It's so cool to not have the endless back and forth of an e-mail exchange. Instead, you can hammer out a complete solution to a problem while chatting live in the channel.
A case in point was yesterday, when someone named 'charmeleon' wanted to create a NetBeans Platform based application that includes the "image" module from the NetBeans IDE sources. That way, he'd have a starting point for his own image-oriented application, since he'd not only have the NetBeans Platform, but also the sources of the "image" module.
Had we been communicating via e-mail, it would have taken weeks, at least, to come to a solution. Instead, we hashed it out together live, including some very specific problems that would have been hard to communicate about via e-mail.
In the end, I made a movie showing exactly the scenario that charmeleon was interested in:
And, right now, in the #netbeans channel, charmeleon said: "NetBeans RCP feels like cheating once you start getting over the hump." I'm sure the fact that the hump was handled within a few hours of chatting on irc is a big contributor to that impression.