I've been to the midnight releases for BC and WotLK and I enjoyed them both. I am also planning to go to the Cata release to keep the tradition going
The thing I enjoy about goign to them, besides getting back home and get an hour of play in before sleep, is meeting all the different types of people that show up.
When BC was released I found the people at the release were alot more 'social' and seemed to talk to eachother more. With WotLK I didn't really see/hear people mingle with one another but that might have been since I was at the front of the line so I wasn't in amongst it all.
So what about you guys? What do you enjoy most about going to the midnight release for a WoW expansion, or if this is your first what are you expecting from it?