Crazy beautiful view, but worth $40... I don't know about that one. It wasn't busy when I went (Sunday morning in January) so I was able to easily get through the whole thing in less then 15 minutes. It was cool because of the glass bottom floor but this is definitely something that you would only do once, or when you have visitors in town.
If I did do it again, I would definitely eat in the view restaurant because it includes free admission!