Saw it a few hours ago, @ the same theater I believe I saw Avatar in 3D years ago.
Very high production value, as you'd expect, but I came away feeling I missed something.
Like others have posted, the 3D is natural; but it was so natural to me that I completely forgot I was watching a 3D movie...and not because I was so drawn into the movie by the plot or characters. Every now and then, there were "depth" cues, but nothing that (IMO) made the story/movie just that much more of an experience in 3D...unlike Avatar.
But I suggest everyone see it for themselves. I enjoyed the movie, but as a few here or elsewhere have noted, it didn't (again, IMO) really bring anything new or thought-provoking to the ALIEN franchise table; but the plot and character actions do raise many more questions within the context of this movie. Perhaps that was the intent. With me, there was no identification with any of the characters...so as one poster commented, I felt nothing good or bad for them as they went through their individual experiences.
I have to admit though, the sound @ the IMAX theater I attended was pretty decent overall...not my usual experience...but it was still a little shrill. I'm guessing they @ least made an attempt to properly set up/equalize the sound for this particiular presentation beforehand.
As with Avatar (again, same theater), the DLP picture was very sharp & bright; with no screen door effect once the movie started. As one professional reviewer stated, the movie is definitely better than the 2nd and 3rd sequels.