I went in 2003 and it was incredibly fun! My class went to the ESPN Zone first until the park opened late at night. They closed the ESPN Zone for all the seniors that night and we were given free food and free game cards. They also had a section closed off for dancing and music. We did have a dress code for when we went into the park... it wasn't too strict... just appropriate.
We spent about 5 hours in the park and it was great, luckily not too long of lines and we were able to do almost everything once. Unfortunately this was during the time Space Mountain was being redone... but almost everything else was open. They had souvenir carts around and a few stores were open. What a fantastic experience, it was something I will never forget!!!