I seem to remember there being something, but maybe I'm having a false memory. A forum search only turned up a never-released work-in-progress called Hellollo, which was last heard of in early 2010.
X-Chat works well, I've used it quite a few times. However, the minute someone makes an IRC client with a scripting system as fun as mIRC's, I would switch.
Oops, yes, I didn't actually realise about Xchat. Thanks. Seems to work very well. I just tried IRC for the first time (in order to organize a NetKeen match).