I don't really care about 3D, but the only way to see this on the big IMAX screen was to see it in 3D.
Far and away the best 3D film I've seen.
I think I've only seen 3 (Up, The Avengers, and Prometheus).
They were all very good in 3D, but this time I literally felt like Michael Fassbender's face was within reaching distance...
That being said, as long as you take the "Alien" element out of this movie, it's a really good sci-fi thriller. I guess it sets up for a sequel, but who knows...
Okay here's some things I'm thinking about in spoiler tags.