AdiIRC is an IRC client with multiserver support and a customizable interface. It offers all the standard IRC features including private chats, basic Identd features, system informations, SSL, IPv6, chat logging and DCC Chat/Transfers. It also offers now playing support for various media players, advanced scripting, themes, MTS themes, plugins, and dockable/undockable activity monitors that lets you monitor many channels at once. The program stores all it`s settings in text files and does not require an installation.
Finally, after trying the top 5 most popular IRC clients for Windows I found one that's just what I need. I will not mention the others by name but this AdiIRC tops them all. It's free, it's slim (small download), has SSL support, it's fast, has slick UI with plugins and themes, it's stable (been in development for over 6 years). These are all features that I was looking in other clients.
Cons
The only negative I have to say about AdiIRC is that it was hard to find on the Internet. In most comparisons of IRC clients, AdiIRC is not even mentioned.
Summary
This is a very nice and slim IRC client, that in my opinion beats all other IRC clients (including both freeware and shareware clients).
A good free IRC client
dragonquest
Pros
Its a pretty clean product - free, no nags, no ads, no spyware and is pretty light on the system being only ~450k in size. However you do need the .NET framework to run it. Good thing is that if you don't have it, the installer will download it for you. The client has all the basic features you'd expect from any decent IRC client. Plus it has Winamp support which is cool if you spend a lot of time listening to music while chatting. You can control Winamp from the client only, even launch it.
Cons
Its just not as polished as mIRC. Plus on launch it has an annoying QuickConnect window with the server options always being the default ones whether you visit it or not. The interface is pretty plain and could be better.