1. Do yourself a HUGE favor and buy your Express Pass online before you go. It's good for 2 years, so even if you don't have time on this trip maybe you can use it another time (that was our thinking anyway). Yes, costs way more than the regular tickets...but you won't have to wait in line for 3 hours (seriously!!!) to go up to the top of the building.
2. If you want to go to the 102nd floor, buy the tickets before you get to the 86th floor (they do sell them up there) so you can at least have a souvenir 102nd Floor Club ticket stub because....
3. The 102nd floor is small, ugly, and cramped (though I think they are remodeling it). It is not open like 86th floor (and the windows create reflections and are smudgy). The view is similar to the 86th floor. So, unless you like to spend money needlessly or you just want to say you went there, then by all means, go; otherwise, skip it.
4. It's lovely to be up there at sunset, but extra crowded, I'd imagine. It was when we were there.
5. I have to say it again: feel like VIP when you are zooming through the line past the hundreds of people who have been waiting for hours (and then you zip right up and cut right in front of them onto the elevator--because you got the Express Pass!).
(Tilt-shifted photo from the 86th floor)