This is very cool.
Been to all the observation decks in NYC over the years and this is by far the best.
Firstly, its floor to ceiling unobstructed glass unlike some of the others. The glass is clear and unreflective (unlike WTC) so no reflections.
It's also bang in midtown, so you have the most spectacular view of the Empire State Building. None of the others can boast that.
It also has a number of other gimmicks that on the face of it seem silly, but genuinely add something fun to the visit even as a 40 year old man includes a glazed floor, mirrored walls, art installations, mirrored balls (you have to see it) and an external lift.
If you're thinking about this or World Trade Centre deck it isn't even close. Do the Summit and if you want to do 2 do Empire for the history, but do Empire first as Summit will blow it out of the water!.
One note though, it is quite warm inside, even on a cool day in October. I wonder if it gets really hot in the summer.