From Businessweek’s 2011 profile of Scott Forstall (a full year before his ouster):
Some former associates of Forstall, none of whom would comment on
the record for fear of alienating Apple, say he routinely takes
credit for collaborative successes, deflects blame for mistakes,
and is maddeningly political. They say he has such a fraught
relationship with other members of the executive team — including
lead designer Jony Ive and Mac hardware chief Bob Mansfield —
that they avoid meetings with him unless Tim Cook is present.
Then there’s the other Forstall, the one former colleagues say
wielded his relationship with Jobs as a bludgeon to expand his
authority, and sent other talented execs packing. These include
iPod chief Tony Fadell, who they say left Apple after clashing
repeatedly with Forstall, and Jean-Marie Hullot. The CTO of
Apple’s application division until 2005, Hullot, according to two
people familiar with the situation but who weren’t authorized to
speak on the record, left the company in part because he was
unwilling to work with Forstall. Hullot, now CEO of Paris-based
photo-sharing site Fotopedia, declined to comment on why he left
Apple other than to say he was ready to try new things.
Forstall seems to engender one of two completely opposite emotions
in people that have worked closely with him. Many rave that he
works tirelessly, endures constant pressure, and has a
comprehensive view of what’s happening in the industry. Others
have a more visceral reaction to the mere mention of his name. Jon
Rubinstein, a former iPod chief who left for Palm in 2006, chatted
amiably at a Silicon Valley party last month, until Forstall’s
name came up. Then he turned away abruptly. “Goodbye!” he said.
I’ll add this: I know a bunch of people who worked under Forstall on iOS — engineers, designers, and managers — who loved working for him.