Well, I'll be buying, that's for sure.
My wife and kids actually went to one of the midnight openings (I couldn't -- had to get up early on Friday....)
The kids -- in their own -- worked up costumes for themselves. Middle son already bears a strong resemblance to Mr. Potter, and thus assembled a quiddich costume. Daughter decided to be Moaning Myrtle.
And of all the kids there, youngest son was the only one dressed as Malfoy. It was downright scary to see how much he resembled him....