Certainly the best acting I've ever seen from Sandler. It certainly rivals his role as a depressed and unstable romantic in Punch Drunk Love.
What the Safdie brothers were able to do in this movie was amazing. For how hate-able of a character Howard is, they're able to fool the audience into feeling empathy for him.
The grit and hustle of the diamond district is clearly visible in the cinematography, it finds a balance with the determination of Howard to finish his goal by any means necessary. Boastful - but not flashy. A happy medium in the sense that the style is present but not overbearing.
This is one of those rare movies that allows you to become consumed in another world. Every moment is anxiety inducing, every decision is poor, and every time you think that you're in the clear, the brothers pull you right back into the same sweat-dripping, wide-eyed panic that you feel in nearly every scene from the opening credits.
It's a good movie, and even though Sandler didn't get his Oscar, it's proof that he's more than capable. I loved this movie.