It doesn't effect human controlled QB's
It only effects the performance of CPU QB's.....
For example this is a created version of Peyton Manning in NCAA 10....now with default rosters you don't see the CPU under pressure throw the ball away out of bounds.
Manning with 96 Awareness on my roster file last year would avoid throwing the ball in coverage and just throw it away
http://www.easports.com/media/play/video/20848898
Awareness also helps in the pocket they will tend to side step a pass rusher.
It's a real subtle move that goes unoticed when avoiding the pass rush but a move that most of EA's default QB's don't do enough of because they lack pocket awareness
http://www.easports.com/media/play/video/20848861
Instead we get QB's who force throws into coverage or they have dumb animation where the ball goes flying up in the air for a INT by the DL.
Awareness tends to make them see the field better vs the Human controlled defense and allows the CPU offensive play calling appear to be smarter only because the QB is doing more of the right things in the game on the field for his team.
Awareness can be utilized to create smarter Option QB's they recognize where the defender is more often and when to make the pitch....there are a few other ratings that tie into creating mobile QB's in which most people tend to think it's just speed and acceleration.
A really good Option QB needs to have his Ball Carrier Vision Rating, Elusivness Rating and Agility Rating and Awareness rating all rated properly in order for him to be effective in the game on the field vs a HUMAN controlled defense.