Irssi is a great terminal-based IRC client. I'd been meaning to switch to it for awhile, but couldn't be bothered until my ZNC bouncer's config got wiped out, and I would have had to poke around Pidgin to get it working again anyway. So instead I took the plunge and I've been using Irssi for about 3 months now with basically just default settings. I haven't regretted it for a minute.
I recently decided to put my various config files (dotfiles) in git, so as to make them more easily portable (and shareable): https://github.com/ergonlogic/.dotfiles
I'm relatively new to quite a few of these program (irssi, mutt, awesome) so I'm finding myself spending a lot of time figuring out how to configure them to my liking. I'd say I'm only about 60% of the way there, but it's still miles better than the alternatives (pidgin, thunderbird, gnome).