I visited the WTC observatory a couple of weeks ago. Wasn't that impressed to be honest though some things are quite impressive such as the film in the lift and then the introductory film.

But too much trying to up sell - the ubiquitous photo in front of a green screen (hello there is a view out there use that!) for example or $15 to rent an ipad with a fancy app.

Much prefer Top of the Rock which is always worth a revisit. WTC is very much (to me) a visit only once place.