Sorry that you're going through this,
djorbs! This isn't fun.
Obviously, it's 100% worthwhile to appeal in a situation like this. Sometimes, scores get cancelled because of things that are misinterpreted. For example, maybe you were talking to yourself, and they thought that you were talking to somebody else in the room. Maybe the internet connection was glitchy in a way that COULD be a sign of cheating -- and obviously, it wasn't. Maybe you had a VPN running in the background or something.
Anyway, actual humans at GMAC read the appeals, so explain your position in as much detail as you can, and pray for the best. But definitely appeal.
Lost in the shuffle here: you freaking crushed the exam, and that's awesome. Even if GMAC denies your appeal, you're a badass, and good things will happen on a retake.
Keep us posted, please!