There are in the thread that StatRacket points out above. Mainly concerned with movement (which will be improved with time in the gym and overall development). But there are other stupid ludicrous claims like he hits with no topspin. LOL nick rips his forehand with heaps of topspin which is why he can hit it so hard and keep it in. The grunting and the emotion is part of his game, love or hate it. I think its an awesome aspect of his game and fits right in with his energetic and fiery character. Regardless of what is said, it was his first slam, he is 18 and the first set and start if the second was competitive against Cilic - with nick not playing at his best.
Ignore the ludicrous comments that people make in GM. Most of them will never ever dream of achieving what Nick has achieved and they're obviously going to criticize despite seeing nothing wrong because that's what they do. They hate.
I really love his battlecry, I said so earlier in here. It shows me how much he's into the game, how much he feels the tension.
I'm sure his second Grand Slam is going to be even better, since it's gonna be on a surface he likes more (Wimbledon?).