AOL has been on the internet just about as long as I can remember so you'd expect AIM to be a pretty decent instant messenger. However, the proof is in the pudding. Nowadays, MSN Messenger and Skype users far outnumber AIM users which shows that at the nd of the day, it's not one of the heavy hitters. AIM was, however, one of the first to incorporate voice, video and desktop-to-mobile messaging and so should at least be given credit for pioneering this technology.
The instant messaging list on AIM has space for 500 friends and enables you to organize your chats and status messages easily. It also allows you to send bigger files than most IM services. AIM's video conferencing function is however much more hassle and it's not immediately obviously how to start a conference until you scroll through the menus. AIM also features it's own e-mail service although obviously, you need to sign up for an AOL account to use it which can turn into a long drawn out affair in itself.
There's no real advantage of using AOL's IM mail compared to others apart from the fact that it does feature a handy "unsend" function if you've sent an e-mail in error. Of course, there's the obligatory SMS function although this is limited to US users and if your phone supports it, you can also use AOL messenger on the move.
AIM is a bit of a disappointing effort from one of the originators of Instant Messaging but still has a few redeeming features that make it worth a try.