His transfer dealings have been appalling all told.
Getting Pep is fantastic, but his biggest mistake was not fucking Pellegrini off after last season.
I think his, or the club's, biggest mistake is being too nice and respectful of other clubs and not having the ambition, or belief, to doggedly tap up, pursue, and ultimately pay whatever it takes, to get serious world class quality signings to improve the first team year on year.
Given our purported ambition, and outlay on some average (at best) players, in my opinion, if we really want to match Barca, Bayern, et al, and smack down every rival in our league, we should be paying agents, clubs, players, whatever it takes to get Bale, Neymar, Hazard, Pogba, Alaba, even Messi. Not all in one season, obviously, but that's the quality we should relentlessly pursue each summer, even if their club says no.
Money talks and agents (and most players) are very greedy. For what we've spent on Mangala, Fernando, Bony, Navas, Otamendi, Garcia, Sinclair, Willy, Kolarov, Jovetic, and other average/shite players, we really could have had 2 or 3 of the top players in world football. We should bully everyone in the transfer market. If we do, teams like Leicester wouldn't be 9 points clear, and teams like Norwich and Villa wouldn't hold us to 0-0.