I saw Matilda on my last trip to NYC, on May 17th. As others have said in this thread, all of the kids sitting around me were perfectly well-behaved - it was the adults who were problems. We were sitting in the third row of the mezz - great seats - and before the show, a steady parade of people kept posing in front of the first row of the mezz for photos with the set behind them. I was under the impression that this was a big no-no, but no one stopped them. Then, during the show, the large group near me all had snacks and the adults were passing them back and forth. I just really wish that theaters were not letting people have food at the seats, but it seems to be almost everywhere now. Note that the KIDS were completely engrossed in the show and did not want/need to eat anything! Can people really not get through an hour and a half without eating?!
The worst, though, was the couple in front of us. The man fell asleep halfway through Act I - well, at least he didn't snore

The woman apparently got bored, and actually got out her phone and started checking her messages or whatever. I gave her about five seconds and then leaned over, tapped her on the shoulder and said "Would you please not do that?" Fortunately, she immediately shut it down - but seriously, come on. I can't believe people don't realize how distracting that light from the phone is.
I guess I should be grateful that at least at that performance, I didn't hear a lot of cell phones going off.
My other experience with bad theater behavior actually happened here in Rochester, NY, when I went to see "Phantom" with a casual friend. This person talked through the entire overture. For me, the show starts when the overture starts and I do not want to talk through it, I want to listen to the music! I had never been to a show with this person before, but now I'm forewarned.
Maggie-the-schnoodle