Christian Bale is such a horribly one-dimensional actor, he's very good at his one dimension, but was badly miscast in this.
As a man who has been targetted by machines since before he was born Bale on paper fits the part of a tortured soul who's had a hard life, but as a guy who has been helped by machines in T2, T3 and TSCC you'd think he'd be a little more open to the idea of a machine who said he didn't want to kill him. For this John Connor to make any sense you have to disregard every other portrayal of the character that there has ever been.
There were no twists in this, everything was predictable, one-liners like "I'll be back" were forced in for no good reason and were totally cringe-worthy rather than a nod to the earlier films. Stuff like that worked in T3 as that never took itself too seriously, this was the opposite and really hurt itself by being too serious.
The only other problem I had was that the resistance seemed to have no problem in beating the terminator bikes and you kill a T-600 by stabbing it in the neck, in other Terminator movies it took the entire film to kill one of them, in this they took them out with relative ease, the resistance should have won ages ago really.
If you take John Connor out of it, it's an OK action film, the other main characters were decent apart from Kate, but she was barely even acknowledged as existing and Bryce Dallas Howard is so wooden that it was easy to ignore her. Not all bad, but the 4th-best of the Terminator films.