I know a guy (Josh) that just tighten's up and rocks the AMU in, almost, a Legend's Awakened build!
He top cuts (or misses on resistance) in every tourney he enters.
He's like a die-hard AMU user.
The point being made in this thread are...
some deck matchups that a Popular now would make it VERY frustrating for an AMU player:
G&G = If they get the lock going BEFORE you, it's over.
Gyrarados = W/o Snowpoint, it's 7 turns = 6 prizes for G'dos
Gengar LvX = they can pull up a LvX every turn which means you may not even get one blast and let's not even get into Shadow Rooming...
LuxChomp = Lux and a Bat can pick off anything it wants. So, you may never get to blast here either. Luxray, itself, can Bright look and KO any non-leveled pixe to greater slow your build (don't forget that they'll spray those Uxies and Mesprits!)
You MAY be able to finese your build and make it work for you. Many have ran and succeeded w/ AMU inspite of the theorymon cautions.
I think people are saying "if you're going to take the time to build, practice, and fine-tune something, why not work on something that has less matchup problems?"