I've had this installed for a couple of weeks, with moderate usage, and I think it's a great feature.
However, I did experience the same problem as Dam Yankee did earlier in the thread, of the whole forum appearing inside the window when logged out. I found though that quickly resloved itself, and must have been something to do with cached pages.
Also, the option to make it viewable only to members totally disables it, with just a ill-sized login option, which doesn't solve the problem if you try it. I didn't place the shoutbox in the info centre, but rather used the shoutbox tag, and placed it in a side menu, if that helps with trying to reslove these two issues.
I left out the whole of the code that should have gone in BoardIndex.pl. - Could it be that I should have kept part of that code, or moved some of it, and that's the cause of the bugs?
Great mod, but still needs a couple of tweaks to work perfectly.
I'll continue to run it though, bugs or no bugs.