I liked X3: The Last Stand, but for such an epic-feeling movie, it should've been longer -- namely, w/ more time spent on the actual character development, since there were so many characters.
There were so many characters and so many things that they could've explained a quite a bit more so than they actually did.
Though, that issue shouldn't stop anyone from seeing this. The movie's still quite good, but it's not as good as good the other two films.
W/ more character development and some of the stories a little more fleshed out (like say The Phoenix story), X3 could've been great...