I just got back and was really impressed. The visuals of the film were magnificent and didn't feel excessive- they matched the theme of the story. Even if the story was a dud the visuals alone would've sold it because they created a real, creepy world and at other times filled you with a sense of awe.
It seems to me that the story is what most people have been torn about. I loved it. I liked that it was ambiguous and I liked that it left you with some questions. Could it have been deeper? Yes, but this is a mainstream film and it did a lot more than most mainstream sci-fi films do so I was satisfied. I'd say it was as intelligent as the original Alien.
There are a few things that irked me, such as Shaw not being as upset about David putting an alien inside her as she should've been, but the general chaotic nature of the ending did excuse the questionable plot points somewhat.