the ESB is a pretty popular place, particularly in the evening when the millions of Christmas lights in the city make for a spectacular view.
we went in the late afternoon and spent about 90 minutes in the queue... my husband went back a few days later early in the morning, at opening, and could walk straight through.
be warned... it is freeeeezing up there!!
but, an experience i would not have wanted to miss out on!
enjoy your trip!!
PS... try to get to the ice scating rink in Central Park... and the Christmas tree in the Rockefeller Centre, and the Coca Cola shop on 4th Ave, and, ... sooo much! :D ;) ::)