O(5) checks it almost every time she walks by it, and when there is something in there, she screams with excitement! It's like Christmas (but she's really much more excited than I've ever seen her on Christmas morning!) every time! I don't want the excitement to wear off, so I only put things in there every few days.
Today, I put a box of Teddy Grahams in the mailbox (since it's "B" week, and we're reading We're Going on a Bear Hunt with BFIAR). Both girls were thrilled, and it was so much more exciting than me just getting the Teddy Grahams out of the pantry for a snack.