I went in with low expectations, avoided previews, and didn't know the twist. So my son and I actually enjoyed it. The beginning was especially fun to watch after having shown the kid the original Terminator for the first time the day before.
That said, the choice of villain didn't work. At all. And it pretty much screws with the rest of the series' importance.
Also, how did the villain go back in time? I though there were a very limited number of uses of the time-travel device, which is why you only ever see a couple of terminators in each movie.