I wasn't a big fan of the first two, but I really despised this one. I think they could have taken the scene of Jean Grey flying out of the water like she did waaaaay back Uncanny X-men when after piloting the spacship back to earth and landing in the water she flys up screaming about being power and life incarnate as Phoenix, shown Professor X doing some tests on her and saying she's fine, then basically lifted the entire original Dark Phoenix saga from the comic books, starting with the introduction of Kitty Pryde all the way through to Jean's death.
That's how I would have done it. Also, I can't see Magneto treating Mystique like that, and I can't see Mystique taking that for him either.
I saw the movie today and enjoyed it. Liked the fact that they finally portrayed the Danger Room, though I'd rather it have been lower tech instead of a lift from Star Trek. Enjoyed seeing the fastball special and a bit of a Sentinels tease. I'm hoping the presence of Bolivar Trask means they'll bring in the robots for the next one.
And the Ghost Rider trailer looked pretty cool.