Battlefield 4 Open Beta - Nvidia Surround - GTX 670 3-Way SLI: Here's a triple-monitor tour of the Siege of Shanghai map in the Battlefield 4 Open Beta. Conquest Large game mode, maxed out textures!
In reality you see maybe a half of the side displays, and even those are in the "corner of the eye". So it can give you a minor advantage, if you notice a movement there, but human vision is very focused, so you will mostly notice things on the main display anyway. More detailed explanation : http://www.cambridgeincolour.com/tutorials/cameras-vs-human-eye.htm
Unfair? In theory it should give you an advantage, but to me no more unfair than someone else with a more powerful PC who can run the game at 60fps compared to your 20 say, or a 120hz monitor compared to a 60, or a better ping etc...
Or just in game settings themselves even between two comparable PC setups. The Battlefield series, and many other games, have plenty of pretty effects which negatively impact your ability to see other players and objectives which can be selectively disabled. I'm also in the camp of multi-monitor being no more unfair than existing options.
Which ever way you slice it, it always comes to down to player skill. Sure, someone has the ability to see three times more than a single display setup in a setup like this, however, how are they going to apply their own skill in order to take advantage of that ability?
Do you reckon a human fly would be an awesome FPS player? Watches everything from every angle in super-slo motion