Salvation had the same problems that so many other recent movies have had: The main character of the movie was someone we don't care anything about.
Transformers: Shia le-WHOCARESABOUTYOUIWANTTOSEEOPTIMUS!
Live Free or Die Hard: The "I'm a Mac" guy. Go away.
Salvation: That guy who's not John Connor.
Nice special effects, but unreasonable writing, construction, and continuity. I will agree that the picture of the future was well-painted; it was grim and gritty, and you saw the resistance truly fighting against these deadly robots. The problem was that this was tangential to the storyline!
I'm glad I brought my flask to the theater when I saw this movie.