I didn't go either but there was a bunch of people talking about it on 420 Magazine's forums until they deleted everything. Apparently Advanced Nutrients and some others boycotted the expo because Maximum Yield won't let anyone publicly admit that the whole thing is about marijuana.
That's a little dumb if you ask me. It's in a legal state, where they also have the THC Expo and there's plenty of publicly pro-cannabis stuff going on. Times are changing and we can either step forward and push to keep them changing or we can hang back and let all the progress fall apart.