Great art museum - for its small size, it boasts some really amazing pieces, and all of the rotating exhibitions I've been to have been impressive. As others mention, the Hall of Architecture is incredible - those plaster casts are masterpieces unto themselves, and I would be that it is no longer possible to make replicas in this manner.
The current Japanese art exhibit is amazing - the centerpiece is the ivory eagle, created from numerous pieces of ivory assembled into a grandiose presentation.
I usually pass on the performance art or short film displays, as these sorts of things are a bit lost on me. It's good to know that someone will give these guys their day in the spotlight, however, in true Warhol-ian spirit.
Will definitely be back!