I'm not familiar with Christian Bale's work (this is the first of his movies I've seen), but I thought he was flat and wooden as the John Connor character. The Blair Williams character added the only significant plot tension when she released the Marcus Wright character and saw his essential humanity under the cyborgian overlays.
Overall, better than the third Terminator movie, but still mostly predictable, mindless fare. No wonder I don't go to many movies.