I thought the schools didn't see your actual GMAT essays, just the scores.

I got the impression they used it to compare to your application essays. If you get a 3 on the GMAT essays, but write a brilliant application essay, they're going to suspect you hired someone to write your application essay.

If there's no big gap between the score and the quality of your app essay, or if you get at least a 4, I don't think they pay much attention to it. I got a 6 on my first GMAT AWA, but tanked the rest (was sick and had enough energy to get through the essays, then could barely get through the rest, shouldn't have even scored it), and that 6 didn't do anything to help my chances. Too bad. Retaking is the pits.

I think fsar is correct the AWA seems to be an additional writing sample that shows your ability to write under pressure in your own words, but I dont think it is a primary resource for admission. But I have read that a school can request to see the actual writing sample and can use it to compare writing styles relative to your essays.