Short Answer: Nothing. A big fat stinkin' nuttin!
Long Answer: Not much more.
Jonathan here from Cinema Styles and I gotta tell ya: I'm not a summer moviegoer. As such, what I learn from the summer movies I generally learn from my kids as I try to convince them to go see as many movies as possible while assuring them that their mother and I will not die of loneliness without them around. Through them I have learned many things:
1. In big city multiplex theatres, ticket takers aren't very astute. I discovered this about a month ago when my oldest daughter was off to the movies. "Wait a minute," she said to her friend, "I forgot my ticket." "What do you mean?" I asked, "You haven't bought a ticket yet." That's when I learned that at the multiplex (where you buy the tickets on the first level and hand them to the takers on the second level amidst the hustle and bustle of multiple concession stands) one simply has to go get their popcorn first and then flash their torn stub that they bought 37 movies ago as they walk by the ticket takers. See, there's a reason all theatres used to have the ticket taker RIGHT INSIDE THE DOOR. People forget why things are done a certain way sometimes. Those who do not know history are doomed to repeat it, or something like that.
2. Iron Man is so great, oh my god, you totally have to see it right now because... no, wait, The Dark Knight is so great, oh my god, you totally have to see it right now because... no, wait, Tropic Thunder is so great, oh my god, you totally have to see it right now because... no, wait (you get the idea).
3. A good way to get into an "R" rated movie if you're under 17 is to buy a ticket to The Sisterhood of the Travelling Pants. I wonder how many ticket buyers for that movie actually saw it.
4. It's a great time to catch up on old movies. As you know from my movie stills that I post here from time to time to deafening silence I love old Hollywood. And when the kids are away the grown ups will play (and that obviously applies to more than just watching old movies - this is the moment when my kids would go "Eeeeeewwwwww!!!!!!" - and if you don't have teenagers can I just tell you how amazingly entertaining it is to get a reaction out of them, and how easy).
So that's what I learned. Like I said, it ain't much. Now winter, that's a whole different animal. The kids are at home bored to death because "nothing good is playing" and I'm out there seeing everything I can before Hollywood reverts back to the pupa stage of the Bells/Whistles/CGI/ADD Magical Movie Sausage Maker of Summer. Oh, there's good, and even some great, stuff in summer too. It's just that as a rule, it's not my thing. And I re-learn that every summer.