#1 Is it worth the extra $$?
For us, it was.
#2 How long does it usually last each night?
about 5 hours (preparty starts an hour before)
#3 Do adults normally dress up? (I plan to possibly)
Most people were. We weren't, because we're from out of town and had limited luggage space - and we had 3 kids that needed to bring costumes.
#4 What are the crowds like?
We went Halloween day. It was a sold out party, and there were lots of people there, but ride lines were nonexistent and treat lines moved quickly. We didn't do characters. We did get one of the last decent spots about 1.5-2 hours before the parade started...so in that regard, it was crowded for the parade.
#5 Do they have any different activities planned on those nights?
I'm sure other people have answered this, but the treat lines/special characters/some stuff going on in NOS. The fireworks/parade is the highlight for us. It was super awesome for us, and we'll probably plan to go from now on, but we have 3 little kids. I'm not entirely sure it's worth the money without kids who are interested in the trick or treating portion (but that's me.)