My daughter and I purchased a "skip-the-line" ticket for a 6:30 PM admission. One of the staff at the entrance told us, upon my query, that all we needed to do was enter at 6:30, skipping the line. At 6:30, that same staff member told us that that not the case, that we needed to get to the back of the long line. We made numerous queries but he insisted our ticket did not allow us to skip any lines except for the line to buy a ticket.
Once we made it downstairs to the security checkpoint (a 30 minute wait) another staff member asked us why we were in that line and moved us to the expedited line. He indicated that we should have been admitted directly. He did save us 15 minutes or so. so that was somewhat good.
When we reached the observatory the night view was fantastic, though it was a bit irksome that we'd purchased a skip-the-line ticket for extra cost for a sunset view and were delayed beyond sunset. The staff at the observatory seemed a little annoyed at the visitors for not knowing precisely how they should proceed. It was pretty crowded up there but with patience you could get some truly magnificent views. It was a bit unfortunate that there is no outdoor observation deck, but I knew that part going up.
I'd advise being careful with skip-the-line tickets and being prepared for a bit of an argument. Overall, I'd have to say our experience at the Empire State Building was far superior.