Something that has really intrigued me is the Fairy type. So far we know that is super-effective against Dragon, and is not resisted by either Flying or Dark. They probably made it super-effective against dragon (and showed us) to balance it out. This might mean that it could resist dragon as well. If Mawile does indeed become Steel/Fairy, it could even be the first to double resist dragon. The thing I have been most concerned about though, is what will they do to secondary types??? Marril for example, will be Water/Fairy. But what about Azumarril? Dropping the type halfway through the evolution line would be a little redundant, but dropping a type that is already present in a pokémon might go too far.