I didn't really like it. It spent too much time developing minor things and ended up rushing through all the major stuff. I would say more, but I feel it might ruin it for those that haven't seen it.
Yes, I think the disco scene was a bit corny. Seems like this is a real like it or hate it type of movie from what I've read. I liked it, but do agree it was not as good as the first two. Seems like they were aiming this one at a younger audience.