The real problem with ICQ chats is that they are peer to peer. And as such, they often don't work through firewalls. What does work (and this fact confuses quite a few people) is the "who is online" function and many messaging functions.
The second problem is that you have to know each and every person who is interested in joining a chat.
How does a "empeg newbie" join an ICQ chat about empeg (or empeg programming)?
With IRC that's no problem at all: He (or she) just joins the right channel.
With ICQ, he first has to ask someone who is on the chat already to invite him in.

ICQ is great to keep an eye on which of your friends are currently online.
IRC is great for meeting (new) people with the same interest.

cu,
sven

proud MkII owner (12GB blue/green/smoked, #080000113)