Singer has been toying with the idea of returning to the X-Men universe for a very long time, and was considering enrolling with First Class back in October. While some fans were holding out hope he'd return with Fox's Wolverine sequel (after all, X-Men 1 and 2 were largely Wolverine movies anyway), but a lot of readers felt he belonged on some kind of X-Men reunion. Having him handle the early years of Scott, Jean, Beast and Storm seems natural. All of the scenes set in Professor Xavier's school were handled very well. They were fun without being childish and corny.
Lauren Shuler Donner described the prequel as just that -- funny without being stupid, noting that they were looking at the darker Harry Potter installments as a model. Since it's being set in the past, I wonder if it'll be set in the 1970s or 1980s? Wouldn't it be great if every frame looked like a Chris Claremont book right down to the neckscarves and sweater sets?