I've seen plenty of "magic" in preview performances. PLENTY.
Is it sometimes NOT as polished as it MIGHT be several weeks later? Sometimes. But not often enough to change one's entire experience.
Is it "wrong" of the producers to charge full price? Yes, I think it is...but as I've never felt ripped off by a preview, I don't have much to complain about. There are only two shows I can think of that my experience MIGHT have been considerably different had I waited longer would be: Shuffle Along (I saw it right before the hiatus) and Spider-man (first version they put out there). I do think I may have enjoyed SA more....but I cannot imagine that Spider-man really got better. Two shows over the dozens and dozens I have seen in previews? Not too shabby, certainly not shabby enough to "warn" people against previews.
If we're not having fun, then why are we doing it?
These are DISCUSSION boards, not mutual admiration boards. Discussion only occurs when we are willing to hear what others are thinking, regardless of whether it is alignment to our own thoughts.