Amazin Caucasian, there is not question about the MX518, if you are playing a lot of FPS, and since you mentioned AA, Im guessing you are.. then this is the mouse for you.
I recently purchased it for my new build that is coming together and I took it out of the packaging to give it a test drive on my old computer, and its amazing. Just get this mouse, you won't regret it
The mouse lets you adjust sensitivity on the fly, which is really cool, I tried it on CS:Source the other night and its a really neat tactic you should try. When you are just using a rifle, turn the sensitivity up higher how you like it, but when you pick up a sniper that has sights, with the click of a button you can have lower sensitivity just like that! And it really helps stable you when you are sniping.. that is just one awesome thing about this mouse!
Highly Recommended!