If you hadn't been paying much attention to the press surrounding this movie, I think the beginning may have been a tad confusing. It shows a death-row inmate in 2003 signing a form to donate his body to science (read: Cyberdyne) after his impending execution. I think some people who just came to the movie blind, may have thought they walked into the wrong theatre.
As a whole the movie delivered. The action scenes were pretty well spaced out. You didn't have lots of down time between them, but it also wasn't non-stop action devoid of character development. Some of the newer characters (aside from Marcus) weren't explored in the depth that they should have though.
Where this movie really succeeded, and many other prequels fail (is this a prequel or a sequel? Damn time travel), was to show the characters we love from the previous films in a manner that was consistent with their previous portrayal. This was especially evident with Anton Yelchin's job as Kyle Reese. He really captured the Kyle we saw in the first Terminator, complete with the compassion you rarely see in gritty sci-fi heroes.
The one feeling I couldn't shake throughout the movie is that I was watching a World War II movie, but with androids. The shaky camera style was very reminiscent of Saving Private Ryan, and became distracting at points. I'm not sure if this was intentional or not, but for my taste, it wasn't completely successful.
Overall, I'd say this movie is successful for what it is. It was fun, the action scenes were solid, and it brought some beloved characters back to the big screen. Sure, this doesn't rank up there with the first two Terminator films, but it's a fun ride anyway.
Rating: 3 out of 5