I hate AIM, it's the ugliest piece of annoying software I've ever used. It's inconvenient for a message to just pop up on the screen when you receive it, and equally annoying for it to flicker in the task bar when you receive another message from the same person.
I still use it though, but that's just because it's the only way that I can contact GirlFriday outside these forums (as well as vi_edit). If it weren't for them, I would not use it at all, this software is straight from hell.
ICQ on the other hand is of much higher quality, although it does have alot of nice features which some people seem to despise. I've been using ICQ for about 4 or 5 years, and I've never been 'switched', because no other software is as satisfying. I've tried MSN Messenger, AOL Instant Messenger and Yahoo Messenger, and they all pale in comparison to ICQ.
-RSI