Con: The title.
Pro: Stuff blows up.
Con: Computer graphics when Sabretooth runs on all fours.
Pro: Fight scenes.
Con: Attempt at a plot failed miserably.
Pro: Attempt at a plot is just a way to justify action sequences.
Pro: Deadpool*
Con: Deadpool*
Pro: Introduced to new mutants
Con: Most new mutants are basically cameos and are often very different than comic versions.
Pro: I've always liked Gambit's power.
Con: Why doesn't Gambit have an accent?
Pro: Did I mention stuff blew up?
Con: Holding arms out while looking up at the sky and screaming. (Did Wolverine just find out Padme was dead?)
Pro: Jackman and Schreiber seem to have put a lot of effort into getting into shape for the movie.
Con: What did they do to [actor's name held back for spoiler] in the escape scene with the kids? That scared me.
Pro: Most of the action was over-the-top and unrealistic. (In a movie where a guy pops metal claws out of his hands, that's allowed to be a pro)
Con: Wolverine butt
Verdict: Bad, but not so bad that it wasn't still fun.
Random note: I realized after writing this that X3 also got a pro/con list instead of a real review, but even that was more thought out than this one.
*I can't really explain that one without a lot of spoilers and an attempt at explaining the plot and it's really not worth it.