Not a Man Utd fan, but even as a neutral I thought he was the wrong choice the second he was appointed. He isn't a winner. Nothing in his previous 11 years at Everton suggested he could be a championship-level guy, and top clubs like Man Utd want to win even in transitional phases.
It just hasn't worked from day one. Botched transfers, players unhappy with training and tactics, mishandling the media. Calling bad performances "good." Making excuses. Getting rid of all of Ferguson's backroom staff, hugely destabilizing the club.
Ordinarily I like to see managers given time but this should've happened months ago. I wouldn't trust this guy with a huge transfer kitty if I was chairman. He's out of his depth. I think he's a good manager if you want a solid, top 10 team. But he's not the guy to take you the extra step and WIN.