Just about every teenager in Central New York (and throughout the USA, I'd say) who's online and uses instant messaging (read: probably 90+% of 'em to varying degrees, depending) uses AOL Instant Messenger. It sucks. Really. Though gaim makes it better.
I'm glad, however, that there will soon be an alternative that doesn't involve having to ditch 3/4 of my contacts and say "use another network or don't talk to me."
I look forward to the day when people can say "IM me at X" and not have to stipulate a network to go along with that (and log onto 1 network instead of 3 or so).