I've gone, but 2007 was my first year so I'm not the most experienced. This year it'll be at the LA Convention Center, which is widely considered a bad idea. It's way closer to me now, but still a bad idea.
In any case, they do get good industry people and the market is pretty great. People have been saying Anime Expo has been declining in quality the past few years, but being the largest anime convention in the country (participant-wise) it's far from suck, so you should check it out if you can.