LINE 1: There's a line to buy tickets. A separate entrance (no line when I was there) for those with advanced tickets. This line was almost an hour long for us.
LINE 2: Then you go inside and stand in line for the elevator. The stairs were closed when I was there recently. I don't know how often this happens. This was a short line.
LINE 3: That elevator to another level (not sure which level we were on, but mid-way up). Then you get in line for the elevator to the top. This was a very long line (45 min?)
LINE 4: At the top, you stand in another long line to get down. (maybe more like 20 min)
I was there on a Saturday evening in February. Saturday night is probably a busy night but February isn't high season. If I did it again I'd walk up to the mid-way level and avoid the elevators and lines! Of course, it was all worth it but it still would have been great if we didn't get all the way to the top.
I'm no expert on ET traffic and your experience may vary, but that's the line breakdown.