Saw it this afternoon... I'd have to say it was decidedly average. It's a fun ride --a solidly entertaining action film/special effects extravaganza-- but I wasn't terribly invested in the story or the characters.
Christian Bale was serviceable as John Connor, but I don't think his character was explored to full potential. It would have been nice if we'd seen more of his personal side, i.e. his relationship with his wife, his memories of his mother... they were only touched upon briefly. It felt like most of the time he was just present to move the plot and action along.
Kate Connor was barely there... a waste of Bryce Dallas Howard's talents.
Marcus was a more interesting character. I would have liked to have learned more about him (like precisely what he did to be imprisoned and sentenced to execution at the beginning of the film), but he was fairly compelling regardless. It might have been better if we'd seen more of a conflict in him towards the end (between the man and the machine) though. I also liked his relationship with Blair... it was certainly more effective than John and Kate's relationship.
I must admit, when I first heard that Anton Yelchin had been cast as Kyle Reese, I was a bit skeptical -- but I have to say, he pulled it off. I actually bought him as a younger version of Michael Biehn's character, and he did very well in the part.
Arnold's "cameo" was fun -- in fact, a few people in my theatre applauded when he appeared. Not necessary, but a nice little touch.
BTW, what was up with the changes to Sarah's "Should I tell you about your father" message? Are we supposed to believe she recorded over the original one she made at the end of The Terminator and added some more info?
The film didn't really explore the unique relationship between John and Kyle as much as it could have. I mean, here we have this guy meeting his father, who's actually younger than him, for the first time, but not much was made of this. I understand he can't tell Reese the truth, but I think it should have visibly affected John more than we saw, despite their limited screentime together. Maybe they're planning to do this in another sequel.
The ending was... predictable. Marcus' sacrifice was reasonably touching (although it might have been more powerful if we'd seen more examples of his supposedly immoral behaviour and/or an internal struggle with the cybernetic parts of himself), but I could see it coming a mile away. The original ending --with John dying and Marcus donning his skin to take his place-- would have been more daring and provocative. I kind of wish they'd stuck with it (provided they eliminated the ultra-dark "everybody dies" part, which was also one of the original ideas).
Ultimately, it's your standard summer blockbuster: entertaining, but lacking in substance. It's no classic like the first two films, but I'd put it about on par with T3 as a decent actioner.
