Missy's failed Danny plan actually had a beneficial side. Since all the cemeteries around the world are now empty, they no longer have issues with plots of land for coffins, for quite some years. Though it's going to require a lot of excavation of the busted coffins and removal of the tombstones before the cemeteries are usable again.
Danny gives up his one chance to come back to life and have a family with Clara; to instead resurrect the kid he killed in Iraq by accident.
Fans joke that Steven Moffat found a way to kill Rory Williams one more time. Seeing as New York City was also a 3W location.
Kate tells the Doctor that her father's biggest dream was to get a salute from him, just once. The Doctor mumbles "should have just asked"; despite his disdain for military protocol, he would have done it as a gesture of their friendship.