It doesn't surprise me. Given that most kids that have grown up with the series probably have jobs or perhaps are off school for the summer, they probably have the freedom to go to a midnight showing. Also, it's the last one, which I think mean a lot of people see it as the big special occasion to go all out for their last chance to see potter in theaters.
Also, IT's HARRY POTTER!>!> @! $OJADP!J
ZOMG!
Can't believe I'm waiting till Monday to see it. I should have my head checked.