I use icq as everybody in my country use it... So this is just to be in touch with friends.. For biz stuff I use msn.
I used icq (2002b) until a couple of weeks ago when I installed vista and had to get a newer version. Sadly the new version really sucks, and has made me move to msn instead.
I still use MIRC sometimes for downloading. When I first got on the internet about 11 years ago I was on there constantly for chatting. I used to use ICQ a lot too, but it's been a few years since I last used it. Now I only use yahoo messenger to chat on.
I use trillian for business purposes. My ICQ number is 379421 if that tells you anything about me and ICQ. Used to as far as IRC goes IRC used to back in the '90's be a pretty good form of advertising, pick a busy network and put up a room and put up a subject for all to see. Anymore I don't think it is used to much except by the ones that are getting on it for a specific reason, i.e. support for a game, keeping up with gaming buddies or friends in general...or by those that have been using it for so long they have pretty much become immune to that type of marketing technique. As for ICQ it was great in it's day, now it's ok to keep in touch with some, or use as a business contact tool...but that amount of spam on most of them is getting pretty bad.