I'm still contemplating the camera thing. If you're caught getting into the arena with they may make you get rid of it. That means wasting away all you're hard work so you can go put it in the car somewhere.
I agree that books are useless, as well as anything with headphones. You'll end up chatting away the day. My suggestion is if bringing a cd player or something make sure you bring one of those personal little speakers and lots of batteries. Or better don't at all.
FOOD, bring as much as that as it is humanly possible to carry (mind you even if you don't eat all of it there will be plenty of hungry people around you).
Water, water, water. Opening night (mind you I didn't even que up for the heart cause there was no such thing, at least no one knew about it) and exactly half way through the show I came pretty close to faiting (though being in a guys shoulder during SBS and only inches away from Bono and his flag might have helped) and had to leave my wonderful spot. So water water water.
The one thing that is really priority to me is light colored clothes, i.e. no black t-shirts the only exception to this rule would be if the weather is cold.
I am personally going to look for disposables of everything I need. Such as cheap rain coat that I can throw away, no purses just plastic bags etc.
IF IT'S A LUXURY, LEAVE IT BEHIND.