Overall, I loved it. Zack Snyder captured the sadness and weight of the original series very well. From the opening fight scene, which was so brutal it was shocking, through the end, everything "felt" right. The credits in the beginning were a highlight of the film, with important moments in the history of the Watchmen laid out with credits floating in bright yellow. The procession from the glory days in the picture above to the sad ends for most of the team was tremendous. As for individual performances, I'd rank them in three levels. Rorschach and and the Comedian were fantastic. I loved the Comedian in this much more than I ever did in the comic (in fact, I'm currently leaning towards the Comedian for this Halloween). Nite Owl and Dr. Manhattan are fine, they look right, and they keep things moving along well. I only snickered at Dr. Manhattan's wang a few times. The weakest links are Silk Spectre II and Ozymandius, as every review has said. I went in thinking they would be awful, and they were not that bad, so I wasn't that bothered. But man, the Comedian stole the damn show for me. I knew I'd love the others, but the Comedian was over the top fantastic.
The sex scenes were pretty darn graphic, with thrusting and gyrating going on all over the place. I have to say that this flick isn't appropriate for kids. I didn't see any at the show, and certainly I think this deserves it's R rating. The violence is over the top and feels a lot like the fights in 300, but neither of those things are a bad thing for me.
I last read the trade paperback about 8 years ago, and I think that was about perfect, since I remembered enough to know what was going to happen, but not to get wrapped up in unnecessary details. I'm ready to see it again. Snyder's shot-for-shot recreation is so true to the source material, you can easily get the same feeling of dread and sadness that the comic engenders. There are only select few things that I think held up better in the trade than in the film. I highly recommend this. I'll be purchasing it on blu.