Sadly, I found that only a few people dressed up for the LARP.
But at Otakon, you can't swing a catgirl without hitting a cosplayer!
In OtaLARP, players have the option of role-playing a character from any manga/anime series. The GMs create a character sheet based on each characters' strengths and weaknesses. Not all of these characters are designed for combat - you could be playing anything from a schoolgirl to a eight-foot tall mech - and not all of them are equally powerful. One of the very first interactions I participated in was between my group, the Turks from Final Fantasy 7, and three or four people playing high-level ninjas from the Naruto canon. A fight ensued, and we got our asses handed to us. The most we could do was throw a punch or fire a gun, but our opponents could summon demons and launch fireballs at us.
It kind of amazes me that this system works at all. Supposedly, pure role-playing reasons should be enough to deter people from using powers to obliterate anyone who annoys them. In reality, people are excited about their fantastic abilities and want to use them - just like in every other RPG on the planet. Another sad fact is that some people are jerks who are willing to derail shared storytelling to stroke their own egos.
But I don't want you all to think it was all bad. I had a lot of fun playing my character, who was polite, well-spoken, and worked for an evil corporation bent on dominating the world. The fact that I'm a silver-tongued devil didn't hurt - towards the end of the game, I pretty much stopped making checks (aka playing Rock Paper Scissors, the equivalent of rolling dice) and just talked things out with people. Most of the players at the LARP were easygoing, funny, and slightly silly - in other words, my kind of crowd. And say what you will, this system has worked for over a decade!
During the game, whenever I was dealing with some jerk in a neon wig I thought to myself, "well, I'll never do this again!" Looking back, however, I realize I had more fun that expected. I think the key to LARP, as with any RPG, is to (a) find a good system and (b) find some good people. If I can make sure those are in place beforehand, I'd definitely try LARPing again!