Linux machine with stable Internet connection + 'ssh' + 'screen' + 'irssi'. Doesn't get any more "Win" than that :>
It's funny... many years ago I started with mIRC, then moved on to X-Chat, and recently gave up on gooey interfaces and went to irssi. I don't think I could ever go back.. clicking things is overrated when compared to the ability to have one IRC session follow me anywhere I go.
edit: fixed for you roci

-kev
re-edit: No, my Irssi is only one deep.. it's by the time I'm on the console of PureTrem that I have to Ctrl-A A A D to detach
