last year it was at the Greatest Bar in boston. I went with a few girls from BC, all of whom were underage. at the door, you either have the option to go in underage, or to show your legal ID and get a bracelet so you can drink. One girl i was with tried to show her fake, a good one at that, and she got called out instantly and was asked to leave. I'm 22 and obviously my ID is real but it's from connecticut so they grilled the shit out of it anyways. The rest of my friends showed real underage IDs and had no problem (obviously)
once the movies are over, they round everyone up that's underage and make them leave, and then the real party starts.
unless your ID is flawless, i wouldn't suggest trying to use it.
Also, girls, they check your bags and shit, so even putting a mixed drink in a coke bottle and trying to smuggle it in does not work.
Hopefully that helps some of you out.