My own rule is that if I am paying money to see a preview, it won't be the first few or even the first week. Comps are another story--like the ones I have for the first preview of Story-Life tonight.
Delays like this happen and anyone who has walked past the Nederlander in the last week knew they wouldn't be ready.
Even when shows are "ready" for the first preview, they aren't anywhere near "ready".
"If my life weren't funny, it would just be true. And that would be unacceptable."
--Carrie Fisher