i dont understand why you should use xfire. theres always aim and other messengers that are jsut lke it so i dont entirely understand whats so special. but yes i do use it, mostly just to keep track of friends and chat. i usse aim for people who i actually know.
Because it's a messenger program geared toward gamers. There are many features which makes it much much better than AIM or MSN or anything else that's just meant for chatting.
If you were to use aim while you're playing combat arms while a friend of yours is playing WoW or something. You'd have to alt-tab all the time to see what he/she said and to respond. Xfire actually works in a game like an ingame messenger. I stated that a little confusing so let me explain more. While you're playing combat arms, you can bring up the xfire chat by pressing whatever hotkey you created. From there you can type a message to your friend without having to alt-tab. Same thing if you're friend is playing a completely different game. All he/she has to do is press whatever hotkey they created and the chat system will pop up in their game and they can reply back to you. And since it's a messenger, you don't have to be in game to talk to your buddies who are battling up ingame.
Another handy feature is to be able to see which of your friends are playing a game and which game they are playing without having to go into each individual game to find out if they're playing or not. I believe if someone is playing a steam game, you can even join on the server they are in from Xfire.
A few things that are cool, but need work is the Xfire voice chat and Xfire video recording.