Christian Bale wasn't too bad, but he should have known all his future performances would be compared to Batman. He did depict the emotional grown-up John Connor that has really aged in the Terminator series. However, Sam Worthington's talent was rather wasted on the "human turns cyborg turns human" concept, and it didn't really play well for this TV-series actor.
Whole film consisted mostly of violently brutal cyborgs blasting humans to pieces, and humans pretty much doing the same to cyborgs. Typical and predictable. Cool CGI, to be honest.
Nothing much more to add to that.
Stop making Terminator movies! The first two were great by themselves!