In general, I'm not a big fan of climbing tall buildings just for the view. The problem is that most such vantage points are a big let down. To me, the best views are obtained when you don't have to look through glass and when you can walk/turn around and get a full 360-view. Such vantage points are typically mountain tops, not tall buildings.
However, there are exceptions. One was a church steeple that you could climb in Talinn, Estonia. They would let you get out on the narrow ledge that surrounded the steeple -- apparently, killjoy lawyers haven't gotten to Estonia yet.
A second example turns out to be much closer to home -- the pedestal of the Statue of Liberty. And as with the Estonian church steeple, you get a view of New York City across the Hudston without being intermediated by glass. Plus, you can walk around and get a view of Jersey City and the Verrazanno bridge as well.
I'm thinking that it would be nice to create a list of viewpoints that are open to the public and afford great open-air 360-degree views. If you know of any others, leave a comment.