Something I'm unsure about -- does GenCon do any type of follow-up surveys to see if people had fun, if there was anything wrong / objectionable / etc. in the game, if everything was explained clearly, that sort of thing? If so, does that get shared with the Event Organizer / GM?
I've had the occasional bad experience as a player, and I sent email when that happened, but when I'm running the game, it's a very different viewpoint. I've also heard rumors of GMs getting bumped / denied if enough people complained (or were no-shows), or non-favored GMs getting shuffled to a crowded horrible room, but that's hearsay.
It may be different if you are part of a gaming group that manages a bunch of GMs, but for right now, I have just submitted games on my own.