Sure, IRC's protocol is simpler, but it's also not designed to support authentication or security natively, or to be federated in a "cross-network" way like XMPP is. It seems that XMPP is more modern, more flexible, and supports real user authentication natively - a win in every respect.
Plus most of the clients people these days use for IRC (Adium, irssi, Pidgin, XChat) support Jabber anyway.
* passwords required to connect to the IRC server,
* passwords required to use given nickname (enforced via NickServ),
* SSL.
At any rate, my original comment came off a bit the wrong way. I'm not trying to say that IRC isn't a workable solution for this kind of group chat system, as it clearly is. I just don't see why using IRC over Jabber (which seems more technically suited to this domain) is a selling point, especially in a marketplace crowded with group chat solutions.
That said, there's definitely room for both protocols and I could see supporting XMPP as well at some point.
Edit: Also XMPP supports UTF-8 for everyhting out of the box and as far as I know it's not really possible with IRC (or did that change over the last years?). E.g. nicks with non-ascii chars are no problem to have..
Why do you think it's not fun?