IRC it's not dead, but it's definitely not what it used to be around 2000-2003. The mainstream chatters have gone to IM and of course social networking sites. Of course there are still the "
"enthusiasts", who can be found on servers like freenode.
So, whereas around 1999-2003 it was used for mainstream chatting, now I think it's more used as a support platform, for projects, communites, just like forums, which are also popular.
Or am I completely off here?

A related discussion, what about the mIRC scripting scene?
Are there still any active sites, besides good old Hawkee?