First Previews on Broadway so far:
The Drowsy Chaperone
The Pirate Queen
Les Mis (06 Revival)
Company (06 Revival)
Haven't been to any closings or opening nights yet, but I do have to say being at a first preview, especially for a new show, is quite thrilling. I'll never forget the first preview of DROWSY - I didn't know much about it, save for the few things I read about it online, it was quite the magical experience. However, I want to forget that first preview of THE PIRATE QUEEN...though it was a real treat to see Boublil/Schonberg in the audience.
In general, preview performances are the most rewarding. Elements of the show can change before the opening night, cast members can be replaced, and your opinions aren't molded by critics (except for the Chatterati, of course

)
<---- You can see the crazy in her eyes. ;-)