Forstall has been called "Apple's chief asshole"[0] - he channels Steve Jobs's approach of being a douchebag, but doesn't seem to have acquired the same level of perfectionism as Jobs.
He also gives me that impression when I see him on Keynotes, one of a power grabbing, back-stabbing kind of guy. Which could or could not be true, I'm talking purely from a "face-reading" standpoint.
The exact opposite of that would be Bob Mansfield.
I've seen each VP (except Mansfield) talk in person and I have gotten a very different impression of Forstall. He was one of the most impressive VPs in my eyes (he talked a lot about his passion for bettering accessibility and making life-altering impacts with iOS).
0: http://www.dailytech.com/Apples+chief+Ahole+Forstall+Keeps+S...