In the summer this place is super busy so keep that in mind when you visit. My husband and I ate at the restaurant on the floor above the observation deck and your meal comes with admission if you want to go down. Even though it was like 9:30 p.m. the observation deck was PACKED. We had to shuffle around to get into spots to view the city, especially the glass floor area. The observation deck is pretty cool and it's worth a stop up here just to see the city from a different perspective. However, since the restaurant above revolves, you can get the same views from the comfort of a seat plus a good meal instead of crowding in with a bunch of strangers for a few seconds look at the city.
The views were great and it's worth a visit at night if you can get up here. The wait for the elevator is long when it's packed so prepare to wait a bunch if you want to get down. We ended up going back upstairs to the restaurant and they let us in to use that elevator since we had been customers earlier. Our elevator stopped on the observation deck floor but we were already full so they wouldn't let any more people in. Wah wah. Just prep yourself for a lot of waiting, shuffling, etc. but it's worth at trip up to see the city.