Originally Posted by Adam why not use an off-site IM system for extended conversations?
I've found that IM systems often aren't directly transferrable to Multi-user chat terribly well. Ultimately though, I don't expect the technology matters a whole lot, but I too would prefer IRC.
IRC has the benefit of having one spot where everyone can gather, whereas (unless I'm mistaken) IM would require planning and coordination of a user chat, thereby allowing exlucsion (or forgetting) of people who may be interested.
In essence, +1 on IRC from me.