The actors did amazing jobs. Noomi Rapace (whom won the Swedish Oscar for "Girl with the Dragon Tattoo) is the lead and Charlize Theron is supporting. That's the one thing that surprised me. Charlize woulda KILLED it as the lead (whom in my opinion is Nicole Kidman with range) and as I was leaving I thought "I bet they offered her the lead and she said no." And don't even get me started with Idiris Elba. He's so smooth and cool it's like he's not even acting just being videotaped. He too didn't have a huge part, but still.
There are scenes that made me cringe. I closed my eyes praying the grossness would be over. Let's just say the ick factor is WAY up, but not how you think. The monsters aren't even as huge of a presence. It's the suspense that got me.
Definitely worth seeing if you like this genre/franchise.