
Based on my experiences at Celebration II five years ago and what my friends who attended Celebration III told me, there have been issues with out-of-control lines and disorganization. Comic Con has been at the convention business a lot longer than even GenCon has but Comic Con welcomes 100,000 people every year (compared to about 29,000 at CIII) and compared to CII, Comic Con is a well-oiled machine.
I know they're trying to improve things a bit by keeping the con open an extra day and a half, opening the store 24 hours, and coming up with fast pass times in advance for those who want to shop there. Still, I know the best laid plans could go off the rails and I realize you're not going to solve every problem if you have tens of thousands of fans who all want to see and do the same things. But I have some suggestions to make things better:
1. Open all of the doors when you admit people in the morning
There's no reason for this stupid system of opening one door for fan club members and one door for non-fan club members. Especially when you realize that 90% of the attendees are fan club members, so it takes two hours to get in every day. Since the half-day on Thursday is going to be just for fan club members, there's no reason for the segregated line business. At Comic Con, there's a line for those who need to pick up passes or buy them, but if you already have your pass, you can enter through several open doors and go have at it.
2. Don't change the rules midway
At Celebration II, they instituted a ticket system for events in the main ballroom on Friday afternoon without telling anyone, so people who had already waited hours in line had to scramble to get them from hapless con workers. Needless to say this caused much strife, chaos, and frayed tempers. Decide in advance how to handle "big ticket" events, stick with it, and make the rules clear to attendees.
3. Keep the store well-stocked, well-staffed, and make sure there are plenty of credit card machines
The Celebration II store was run poorly and so was, according to my friends, the store at Celebration III. My poor buddies back in Maryland waited seven hours in line to buy souvenirs. Stuff ran out early. With the store staying open 24 hours, they need to make sure there's plenty available for attendees, that there are enough folks working there to get stuff quickly for customers, and make sure there are enough credit card machines. At Celebration II there was only one machine! And guess how I paid for all of my items?
4. Make sure convention staff can handle people and that there are enough concessions
The staff at Celebration II were know-nothings who came up with stuff on the fly and seemed absolutely terrified of the whole thing. The 501st did a superior job keeping order. If convention volunteers and paid staff are decently-trained and kept informed, they won't need to rely on costumed fans to do the work for them. Food concessions at CII had looooong lines and on the first day, several stands ran out of food shortly after noon. Comic Con is also cursed with long lines at the concession stands but to my knowledge nobody ran out of food either.
5. Treat the fans like guests not like pests
Sometimes fans have astronomical expectations and when those expectations aren't met, they feel utterly cheated. But I don't think expecting a half decent time is unreasonable either. If things go wrong, make it right for guests to the best of your ability. Don't blow off guests with genuine concerns or problems. Act like you care. It can be stressful to spend a long time in line or to stand in a whirl of sensory overload in a noisy convention.