This is one of the four premier observatories in New York (the others being the Edge, Empire State Building and Top of the Rock). This site allows you a commanding view of the southern part of Manhattan Island. It also allows you to view parts of New Jersey and the entrance to New York Harbor. You get a clear view of the Verrazano Bridge and the Statue of Liberty.
One shortcoming of this observatory is that it is fully enclosed. However, they keep the glass very clean. I took about 70 photos and didn't have any problems. One friend upon seeing my photos asked me if they were taken from a helicopter.
You can get a tablet that explains things as you move around. I found this to be annoying and don't recommend it. There are lectures given every so often on the lower floor of the observatory. You should definitely go to one of these. They are very informative.
If you are in New York, make this a stop on your itinerary.