Mystique is played by the same actor from first movie which is Rebecca Romijn.
The guy who turned into metal is Colossus.
The girl who has the power of intangibility phased through solid walls is Kitty Pryde. She also appeared in the first movie at the classroom scene when Wolverine first met Professor Xavier.
The woman who has long adamantium nails is called Lady Deathstrike.
Pyro is originally one of the villains in X-Men comics which is why he joined Magneto in this movie.
The scenes involving the broken dams, particularly the Alkali Lake dam collapse near the end of the film, were created using a combination of CGI and miniature models.
Next movie reaction is X-Men: The Last Stand (2006).