The thing that irks me most is that van Gaal is so stubborn. He should look at the player material that he has and adapt the system to get the most out of his players, not squeeze the players into his 3-5-2 at all cost. It's not working. United neither have strong centre backs nor great wing backs to make this system work. Also, I think he's trying to be too smart at times ... that lineup against Southampton was a disaster. Really, Blind as a CB? Di Maria up front in the Robben role? Rooney as CM? Sorry, but that was atrocious. That game was extremely important, it was simply not the time to experiment like that.
Also, van Gaals handling of Herrera and Falcao really pisses me off. Herrera is such a creative player, he's simply a joy to watch ... and we all know what Falcao can do, and yet, van Gaal still never drops Rooney or van Persie at all. It's frustrating. He has so much creativity at his disposal, he should use it once in a while.
against strong opposition, you could still go for something like this:
I like van Gaal, but he needs to get his act together quickly and stop trying to be so stubborn. Play your strongest team and play your strongest players in their best positions. It's not rocket science.