ViRC is an amazing IRC client for the Win32 "platform". It is not, as many people say, dead. Those of you using mIRC should try it as having a usable scripting language can be quite handy. Unfortunently, it is rather slow and, for some people, unstable. If you really need both speed and a powerful Delphi-like scripting language, check out BIRC (Bisual IRC), a client designed after ViRC.

For more info on ViRC check out http://www.visualirc.com