Irssi, done the Mac way.

All the features that you know and love from Irssi on Linux (or command line OS X) but with added juice from OS X. MacIrssi will automatically disconnect and reconnect your active connections when you put your Mac to sleep.

No need to have a perl script to interface with Growl, MacIrssi has a fully featured notification system; including Growl notifications, sounds and dock icon bounces for a variety of events.

Revamped Preferences

Since the release of version 0.8.6 MacIrssi has gained a new, reworked, preferences pane. Giving everyone access to a variety of Irssi options, including creating, modifying and deleting servers and networks; bringing initial server creation out of the realms of the unknown for new users. The new shortcut system allows any non-menu keystroke to be mapped to arbitary IRC commands.

MacIrssi also ties deeply into Irssi's preferences system to ensure that your chosen character set is consistent right from Irssi's network stack through to it being displayed onscreen.

Still Irssi underneath

MacIrssi is still Irssi core under the hood, it still reads ~/.irssi/config and read themes from the themes directory, etc. MacIrssi will read any theme you've used on Irssi in the past and give you the look and feel you are used to. Care has been taken not to trample over any of Irssi's commands or settings, if you want to use MacIrssi in the same way you've always used Irssi then everything should work. Even down to Perl scripts, if you are using Mac OS X Snow Leopard (10.6) or higher. (Sorry, this is unavoidable because Perl isn't included in the Xcode SDK's, so I can't compile Perl support for Tiger or Leopard.)