We attended the Exhibition in San Diego last summer. As a TOS fan, the chance to get a pic on the Enterprise bridge was sweet
(The folks running that part of the exhibit were also very cool about photography, just so long as it didn't hold up the next group waiting to come in, etc. I was able to get a close-up shot of me in the chair, and my friend and I working at different consoles, etc.)
We're going to be in Baltimore for a convention in July, and are seriously thinking of going to the Philly exhibit while we're there.