I don't think anyone has worked out what type of player Cleverley is. He doesn't appear to have the composure and eye for goal of an attacking midfielder, he's not an anchor man and he seems to lack one particular talent such as long range shooting or dribbling ability that make him stand out. From what I've seen of him he's the sort of generic midfielder like Webb and Phelan that SAF likes to have in his squad.
To give him his due, when he was on loan at Wigan he did look like he had more class about him than his team mates. And, if there is a 24 year old England international with more than a half century of games for United under his belt going cheaply, we'd be foolish not to be interested. McCarthy and Cleverley could be a really good, young, energetic partnership and he could also give us extra cover for Barkley.
I'm all for trying as get as many promising players into the squad, especially if they're English and especially if they're not going to cost a lot.