I went to see Salvation last night, and I'm simultaneously impressed and unimpressed.
The whole Marcus thing was quite interesting and done fairly well, even if it's not really explained very well. One of the complaints I've heard about this film is that John Connor is secondary to Marcus, but I don't see that this is a bad thing. After all, we know pretty much the whole of Connor's story by now, except the fine detail. I enjoyed the film, and appreciated the lack of cheesy camp compared to parts of T2.
One aspect that started off irritating me, but later surprised me by actually being explained, was Marcus' reasons for acting like a human. Throughout the film, I kept thinking that surely Skynet was too careful to release a Terminator that thinks it's human; the explanation was surprising - not in its nature but in its inclusion. It shows greater thought than I expected from Salvation, and it re-establishes Skynet's cunning, which is something that's been missing for a while.
I also appreciated the appearance of the Arnold T-800. It was obviously just a tip of the hat to the previous films, and maybe a way of establishing some visual link between Salvation and the others, but it was still a nice touch. I didn't expect it, and I was impressed by how successfully Arnold was mimicked.
On the other hand, some elements annoyed me.
The barrel roll of the camera in the crashed helicopter seemed contrived (and I'm not someone who generally notices camera work), it seemed far too easy to sneak into Skynet Central, and John Connor never convinced me as someone so magnetic that the resistance forces would act in defiance of their commanders and the only apparent hope for victory just on his word. Throughout most of the film, Connor is more a maverick soldier than any kind of figurehead or inspirational leader. My first real gripe, though, is the nuke. What the hell is that? Connor detonates several nuclear devices while flying low overhead and no-one in any of the aircraft suffers so much as turbulence? That's the one of two parts of this film that struck me as downright sloppy. The other one is Connor's astonishment. I know he's shocked that a terminator genuinely believes it's human, but he also seemed like he hadn't already encountered terminators in the past. He seemed like he was just now seeing each of Skynet's new inventions, rather than having met a T-800 and and fought a T-1000 in adolescence.
Overall, though it had several faults and seemed to me to have been slightly clumsily directed, I found Salvation a reasonably enjoyable watch. It managed to be an action film without being corny, and it made an effort to stick to the sinister menace of the original Terminator. I'm willing to forgive its shortcomings because none of them were so glaring that they affected my enjoyment too badly.
Now I might have to give the TV series another try. I saw an episode, maybe two, and it didn't grab me at all. It could be worth another go, though, and season 1 is available for a decent price on Amazon.