I was there and it was pretty cool. Hulk came for a little while a few times; he kept pronouncing "pokémon" wrong (as pokeeman). There were some musical performances, mostly by the Pokémon Fan Band, and they put on some little skits with Jesse, James, Officer Jenny, and various other animé characters. The whole thing was hosted by "Cooltrainer Tracey". Then there was, of course, the national championship. The semifinals and finals were showed on the huge screen on stage.
They also had a giveaway where you could get one of the top 20 pokémon ("As voted by fans on www.Pokemon.com"). They were: Pikachu (10th Anniversary Flying Pikachu), Charizard, Zapdos, Bulbasaur (I don't know how it got in there either), Latias, Articuno, Suicune, Absol, Espeon, Umbreon, Blastoise, Latios, Moltres, Alakazam, Entei, Typhlosion, Raikou, Tyranitar, Blaziken, and Dragonite. Only the Flying Pikachu was really worth the wait (over an hour), since you can get all the others within the games.
One of the best things was the Video Game Arena, where you could (after another long wait) play demos of Mystery Dungeon (Red and Blue Rescue Teams) and Ranger. They were both interesting, but really not much more than distractions until Diamond and Pearl come out.
All in all I'd say it was worth all the standing around in the hot sun. It wasn't exactly the "Party of the Decade" as they advertised, but it was fun nonetheless.