Currently the best FPS IMO
I'm pretty happy with this FPS. There is an issue of team balancing that is not yet fixed though people still play. Having the ability to customize your character & gear is something I really enjoy. It makes your lethality unique. Though just as with any FPS, there is plenty of camping/snipers & in some cases people taking vehicles just to destroy them on your team....
Of the two most popular FPS games right now MW3 & BF3, I would say it just comes down to preference with which you prefer. A style I guess you'd call it. I think BF3 would be more for adults were as MW3 might lean towards the younger gamers. But, it's just a guess. Based on what gameplay you're looking to be apart of. I still prefer BF3 over MW3.
The character interaction/interface/responsiveness is wonderful in my opinion.
You may become angry easily if you end up getting killed soon & often when you first play. Try not to get annoyed.