It used to be that PN was more limited, when I was there last year it was every bit as busy as Saturday afternoon. You just get a first look at everything. IMO it's too short (I think 3-4 hours?). A lot of people use it to try to get exclusives, but I gave up on those a few years ago after my whole experience got screwed up because I spent so much time waiting to buy exclusives.
I usually like to go on PN just to take photos of the new toys. But I'm still in line and PN is sold out. Will try to get PN tickets when the general public sale happens.