Hear ye, hear ye! Student developers..

in my opinion, x-chat aqua and colloquy (http://colloquy.info , but the nightly is at http://colloquy.info/downloads/nightly.zip ) are both excellent IRC clients for OS X.
Conversation and all those others are a little too on the n00b-ish (for lack of a better word) side, or they lack features...or they're just plain bad. (of course, I haven't tried every single client for OS X, but I have tried many, and those two are among the best)

Of course, there's always irssi and bitchx, among others.

To fill it out, colloquy is nice for people who know the IRC basics, and who like looking at pretty stuff. Its based off webkit though, so its pretty slow.

x-chat aqua is nice and fast, except its ugly. steve green (is that the x-chat aqua dev?) did a good job porting it, but nothing else.

for people who have no idea how to use IRC or something, and wont mind using a slightly featureless IRC client, try Conversation ( http://homepage.mac.com/philrobin/conversation/ ).

for people who know their IRC and dont want to use something like that, there's always irssi. Get fink or dports, install with the usual apt-get or port install.

for first timers and whatnot, I suggest reading an IRC primer/tutorial. I have one for a different channel that I wrote for all platforms, I modified it slightly to fit, but nothing else really. So if something doesnt make sense, sorry

http://applegoddess.org/studentdev.txt

Thats just IMHO though. YMMV. But see ya in #studentdev! I'm melee (or melee_squared), say hi or something hehe. And get more people to get in there!