The kids really love the Lego store (duh!). They have places you can play with Legos, including a three person table which is for sale. They have some great Lego items, including Lego kitchen ware, magnets, office supplies, and even costumes. The costumes are pretty inexpensive, and we actually bought one at the last minute last Halloween and it worked out great.
They have a birthday party thing which I skimmed the brochure on. It sounds like you pay to have your friends buy Legos, then go to the food court, since I don't think food was allowed in the store. No thanks!
They also have a frequent buyers card that you can only get a stamp on if you buy $25 or more at a time. I think once you've spent $200 you get something. We go there a lot, but don't always spend $25 so it's not helpful for us. But having all boys, we do go there a lot whether we like it or not.