In my mind, the concern would be pressure from Disney on the comics and the movies.
On the one hand it could be really good. Disney can help Marvel enter different markets. Really get their characters out there via cartoons, toys, marketing, etc. More money could mean more titles, more movies, etc.
But more doesn't mean better. I'd be concerned if Disney tries to make the movies/comics more innocent to fit their image. Or if Disney forces certain titles to be canceled before they can find their legs.
Disney owns Miramax. I wouldn't be too worried about them trying to make the films too innocent.