He's excellent. It's probably his last season, at United, despite the fact that Real Madrid are trying to rival United for the most boring style of play in Europe. If Rafael Benitez stays, then he should at least defer his move again, but if not, there's little ahead of him to inspire him. United's best hope of keeping him beyond this season is to make sure that a more interesting manager than Louis van Gaal takes over and persuades him that medals and national team selection are more likely with United. He's been more or less faultless, and kept United in the game with a smart stop against CSKA Moscow.
He got to play against Middlesbrough in the Capital One Cup, in which he kept a clean sheet but failed to convince that he is much more than a liability with the occasional ability to pull off some ridiculous saves. There's not much point complaining or worrying until or if De Gea gets injured, at which point you can imagine that Louis van Gaal will miraculously rekindle his relationship with Victor Valdes.
He's at an age where it is doing him no good to be second or third choice. He should be sent on loan to get experience, but it seems like he's not desperate to do so, and nor are United.
On the naughty step still, and he'll probably be playing for Newcastle United in 2016. His biggest contribution to United might be that he reduces any transfer fee paid for Ayoze Perez by going the other way.