In terms of material:
Ghost - wowza. Caught the national tour, and except for "With You," it was unbearable. Some of the effects were good, but most of them were just Disneyland magic tricks The lead men were not great, either.
Catch Me If You Can - I thought it was just the production, but after listening to it I still couldn't get in to it. The tour was horribly put together and the material didn't do any favors.
Camelot - Likewise, I thought it was just the production I saw (with Lou Diamond Phillips), but the show is just not strong compared to a lot of Golden Age musicals. I fell asleep during Act Two.
Jersey Boys - boring. That being said I'm not a Four Seasons fan, but the show itself was not good, in my opinion.
The Rat Pack - left at intermission.
Pippin, Act Two - how is the second act of a show THAT MUCH weaker than the first?
In terms of production:
Chicago - I caught the national tour about two or three years ago, and it was atrocious. The Velma could not have been less interested, Paige Davis was barely in key, John O'Hurley gave such a beige performance, and Mama Morton served as my only source of relief, hooting and hollering through her number, and spending the show cackling like Ursula the Sea Witch.
"I saw Pavarotti play Rodolfo on stage and with his girth I thought he was about to eat the whole table at the Cafe Momus." - Dollypop