The only surprise is it lasted this long!!
Browlett's well publicised staffing c0ck-ups in the Retail stores were a sign that this relationship wasn't going to last long. If he wasn't pushed (which I think he was), then I suspect his ego took such a bashing that resigning was his only option in the circumstances. He should never have been hired in the first place IMO.
Scott Forstall has also been fired, presumably for either Map-Gate or Siri, both of which have so far have fallen short of Apple's expectations...
http://www.macworld.co.uk/apple-busines ... id=3407920But let's not feel too sorry for him, he's done alright out of it...
On the positive side, Jonny Ive is now also advising on the software UI as well as leading the hardware design, so hopefully that will end this skeuomorphism malarkey in Apple's software. I hope.