Well, I saw this. It was... intense? It was pretty true to the source material, given the constraints of film. I also read the book forever ago, so I only remember certain things. But almost all of those things were in the film, so I can't complain. My g/f basically re-wrote one key scene in the car on the way home and I instantly said, "that would have made it a much better film" so I guess there were certain flaws, too. However, I liked it. I can't say I liked it enough that I will recommend it to anyone except fans of outer space sci-fi stories and fans of the book. But for them? It was excellent.
Homsar: yes, the movie certainly focuses on the psychological effects of war on kids...er, well, on Ender at least. Not much on anyone else.
The actors were mostly good. I thought Viola Davis and Harrison Ford were particularly stiff in some of the early scenes, but later they were definitely good. In fact, I know this isn't possible, but it was almost as if Harrison Ford remembered how to act the further into filming they got. It felt like it even if I know they shoot scenes out of order. Maybe he just had bad digestion for a couple of days when they were filming certain scenes or something. The kids were all great. Hailee Steinfeld really was impressive, and some of the lesser names playing roles of bullies or similar were all very convincing.
It's tough. I wanted to like it, so I did. I am not sure how much bias this gave me. The scenes in the battle room were good, and considering that I had just scene Gravity I'll say that I felt like more of an expert in zero-G than the kids were initially, which was amusing.
In the end I think it'll go down as another movie and that's that. Not great and certainly not horrible.