Huh? Fassbender is a good actor, but he's no better than James McAvoy. His (McAvoy) casting, Vaughn directing and Singer producing were, therefore, the first signs that First Class would be something very different from the mediocre X-Men films released after Singer left. Fassbender is just adding to all this, not "oh, now I know First Class is cool because it has an actor who worked with Tarantino!" or something like that.