Back from lunch, so I can provide some more info on the gaming at Gencon.
This is typically what happens - on the first day, people stand in really, really long lines waiting to register for games. While in line, they're perusing the catalog, looking over all the options, and choosing the ones they want. By the time they get up to the desk, the person informs them that 75% of them are full, and they have to select other options. Pwned!
Instead, I wouldn't worry about it. Like I said, in the past I've gamed very little, and been perfectly happy. There are enough pick-up games, and ENWorlders who are happy to just go off and game somewhere that registering for games is for newbies (IMO).
Then there are generic tickets. If you sign up for games, they typically cost money (like $2.50 for a 4-hour slot). For these, you basically buy tickets and each ticket costs $1.25, so a game requires two tickets. If you just want tickets, but not to specific games, you can buy generic tickets. It typically takes two tickets to play a game, and if a game has open slots when it starts, you can supply the generic tickets and play the game.
Here's the problem - games start on a regular basis, like 8am, noon, 4 o'clock, etc. So, let's say you're wanting to play some game and you've got your generic tickets in hand. You find the location of the game, go and stand around, and sit at the table. The GM shows up, and then asks who has tickets to the event. Those that actually registered for that specific event are given precedence, while those with generics are taken on a first come, first serve basis if there are openings. Sometimes you can get into a game this way, but sometimes you can not. So, if you're standing there at 4:00 (or whenever) and the GM says, sorry, the game is full, I'm not taking any more generics, you're left standing there in the cold. And, furthermore, it's now about 4:15 and not only did you not get into that game, every other game that was scheduled to start at 4:00 has already started, and you're screwed out of being able to play in those as well, so you have to wait until the next time slot, which is probably 4 hours away.
I was very very disappointed in the pick-up games area in '03, but I heard it was much improved in '04 (I couldn't go last year). The pick-up games area should, in theory (this was how it worked in Milwaukee, and it was great) had a guy that more or less organized it. So, you could go up and ask "any games starting?" and he could point you to a couple of tables that had games that were currently rolling up characters, or something and you could go and see if they had more openings. Games were starting up all the time in that area, so it was never a big deal to find one. Or better yet, run your own game. People will just show up to play, and in no short order you've got a full table, and you're ready to go.
Which I think is the ultimate truth to GenCon - those who GM are never short on being able to find a game to participate in, because you can just run your own!
All this talk of GenCon is making me excited, btw.