Great movie when watching it and I really enjoyed it, but if you take time to dissect it, it was actually very poorly done compared to the first 2. They fell into the X-men trap of having too many characters (and if you didn't watch the cartoons or read the comic books) leaving the audience confused if you didn't know whats going on before hand.
So I guess in summary, if you are a movie critic, you might not enjoy it. But I loved the movie for all its downfalls.
And ya, the random humour was very well done (unlike Family Guy, et al)
Kirstin Dunst does a great job in these films. I fall in love every time