This film isn't just bad; it's outright offensive! Everything great about the original films is gone in this dreadful sequel. The script is mindless and often seems ignorant of elements established in the previous films. The CGI is obvious and overdone, the characters are moronic, and the acting is irritatingly bad (Nick Stahl is particularly awful). I've seen worse sequels, but this one hurt me the most.
This movie gets a lot of benefit from being able to look back at it on hindsight, especially after the existence of Salvation. The really long crane destruction scene near the start will still take you out of the movie as much as it did before, but overall you won't really remember what the problems you had with T3 in the first place was.
It's the kind of film that seems to be rushing along to the next action scene, and since Mostow knows how to stage action it is effective. In fact I enjoyed the action scenes so much I would have given this film 4 stars but the attempt at profundity in the last 15 minutes definitely undercuts what was a solid and entertaining b movie.