Man, the extras sound fantastic.
Fuck. If only the deleted shit was in the cut, I'd be all over it.
I totally get why it's not in it, a lot of the scenes work on their own, but in the movie, not sure, the Engineer speaks is a great scene but they cut it, because they want the Engineers to be more mysterious. The Janek fills Vicker scene right after she torches Holloway is cool, but as Ridley and Scalia (editor) say it in the making off, they were going into other directions right after she torches him and it would feel like putting the brakes on the movie.
Fifield attacks with full CG xenomorph-like Fifield is cool, but CG looks a bit ropey in some spots and it's not as effective, Ridley wanted Sean Harris' acting to come through, so they did it with prostetics.
The alternate opening is just 4,5 sec of the old Engineers giving the young Engineer the bowl, and then it's the same as the theatrical version, they got rid of it probably because they want to save some of the Engineer stuff for the sequel.
The scene where the Engineer has a fight with Shaw is cool, and rad, but as Ridley said it, i t diminishes him, being hit by an axe when he's a superior being. The Paradise alternate ending is awesome, with some bit more info on the Engineer's world, but it's different from the theatrical version and in it, Shaw just tells David "Well maybe that's because I'm human and you're a fucking robot" and she shoves his head in the bag instead of gently laying it in the bag.
In the documentary, there are also glimpses of the Engineer walking from the derelict to the lifeboat, so there is even more footage out there, but not sure if it's useful, they cut because it needs to be cut, in their opinion, but often, it's for good reasons.
By the way, something caught my eye several times in the documentary, they were shooting the movie in 48 fps, as it said on the clap thingy, weird that it never got out. Would like to see the movie in 48 fps.