I don't have any issues with people who don't think it's a "wonderful" signing. There's nothing wrong with that. He's not the best of the best.
But I do think people are being too pessimistic. When SAF needs players for an instant impact (which I do think Young will provide) he will generally go for PL proven players (Berbatov, VDS, Tevez, Carrick, Rooney, Rio...). There are exceptions of course, like Vidic and Evra.
But when he buys foreign it's usually on young talent, like Nani, Anderson, Chicarito, and now it looks like De Gea too. Hence why Sneijder was never going to happen.
I think it's a top signing personally. Don't see anything wrong with it at all. Decent price, versatile, good Premiership proven player who can actually take set pieces.
I mean really, what can go wrong?