Okay.
I liked how patiently the origin story was set up. The thing I disliked about X-Men was how it was basically mutants for dummies. They had Xavier explaining the story of the X-Men and the mutants to Wolverine, as if it were a beginner's guide for movie audiences. I personally think that's a stupid way to handle exposition. I liked how First Class let the audience watch the story unfold with Charles and Raven on one side of the equation, and Erik and Sebastian on the other side. You got to learn about the X-Men universe while the story unfolded instead of it being like a mutant version of a high school instructional film about duck and cover or teen pregnancy.
