All of this Microsoft Windows discussion is irrelevant
It matters not a jot whether Microsoft have a history of trademarking generic terms, that is not what is at issue in this case. Just because the USPTO have previously granted trademarks that may or may not be generic does not mean they should grant this one to Apple.
Each case should be judged on its merits, not on the history of either protagonist to the case.
Both sides in this seem to be acting as rational businesses, Apple are trying to create intellectual property which gives them a trading advantage and Microsoft are trying to stop a competitor from gaining an advantage through the creation of intellectual property. Microsoft have a history of being on the other side of the debate, so what? It may be a bit rich, but someone should be trying to prevent Apple from gaining this advantage, so it may as well be Microsoft.