What a great episode to end on and a great review of it. Incredible balance of drama and comedy which has what the show has been all about. After watching shitty after shitty episode for the last two or three seasons, some how the last episode made them all worth watching.
To answer Brian, somewhere I read that Denis Leary did the whole show to commemorate the FDNY on 9/11 and he wanted to reiterate that on the last ep. Definitely saw the parallelism between each event. Who knows, maybe "Go! Go! We'll be all right" was said on that day.