For me, movies like this are almost comedic. Maybe it's just that it becomes a contest to see how much stuff they can blow up. There were a few scenes with plot development, and they almost seemed out of place. C'mon, let's get back to the action! My favorite bits were the scene where Arnold was dangling from the crane, smashing into stuff, and the scene where Arnold and the TX had a fight in the men's bathroom. He busted a urinal over her head. I don't think I've ever seen that in a movie.
I liked the ending as well. So the machines win this round, nuclear war starts, 3 billion people die... but John and Kate live. Neat. The nuke scenes were cool, but not quite as cool as the bomb in 24 this season. That was intense. There wasn't much that was this intense about T3, but it was still a cool guy flick.