It doesn't help me aim any better to be honest, but then again I have had it turned on 99% of the time I play just because it's possible. The few matches I played with it turned off though went pretty much the same way as my other matches, so don't really think it does any good.
I mean absolutely no offense sergio but if you can't tell how much difference the aim assist has in this 2-d plane hit registration, then you must be very new to the game. Of course, this is just your experience with it so it relative. However, if any player who has spent a good amount of time and is acquainted with online shooters, they'll tell you that this game has a ton of aim assist. In my experience, it like night and day with the aim assist. I don't play with it on but when I did, I could rack up quick killstreaks without even trying. It wasn't any fun to me because I didn't have to think when I was aiming because the game did the majority of the work. I get enjoyment mastering basic mechanics BUT it doesn't take much to master the shooting mechanics with the aim assist in this 2-d plane registration. It's always about spraying the most bullets in the target's general direction.
To answer the originial poster in case this prior paragraph didn't answer your question, lol, no I don't use the aim assist. I believe without a shadow of doubt that this aim assistcoupled with the 2-d hit registration makes this game way too easy and bland.
None taken

Huh, well it is a while back I turned it off for a bit and didn't really notice any difference as far as I remember. To be honest as well, I am rather new to FPS games.