Robin van Persie still looks ineffectual
When Louis van Gaal swapped the Netherlands for Old Trafford, many expected him to revitalise striker Robin van Persie, who struggled for form under previous boss David Moyes.
Yet so far, van Persie has scored just three goals in 11 Premier League games, and looks off the pace in virtually ever game he plays. At 31, it looks like the injuries during his time at Arsenal have taken their toll on van Persie, and van Gaal has to be thinking of replacing him already.
United must keep David De Gea at all costs
After a tough start to life in England back in 2011, Spanish international goalkeeper De Gea is proving his doubters wrong - very, very wrong indeed.
De Gea was outstanding against Arsenal yet again, pulling off eight crucial saves to keep Arsenal at bay before being beaten by a superb Olivier Giroud strike. With his contract set to expire in 2016, Real Madrid are lurking in the shadows, and after another superb display, United must do whatever it takes to keep De Gea.
There's still a dedication to youth
When United sold Danny Welbeck to Arsenal, many believed that the club had abandoned their interest in bringing through players from the youth team, especially with fans waxing lyrical about the 'Class of 92'.
Yet against Arsenal, United not only fielded Tyler Blackett and Patrick McNair in their starting XI, but also brought on James Wilson late in the game to see out the result. For all the criticism United got for signing Radamel Falcao and selling Welbeck, the injury crisis at Old Trafford has increased opportunities for youngsters.
Wayne Rooney is in his best form for years
There was a lot of scepticism when Wayne Rooney has made Manchester United captain in the summer, but he seems to be repaying van Gaal's faith now.
Yet after a great international break with England, Rooney returned in similarly great form, sprinting on to Angel Di Maria's pass and coolly lifting the ball over Damian Martinez to hand Manchester United the win. He looks refreshed and willing to take players on again - something we haven't seen for a while.
United are getting there - slowly but surely
Having picked up just one point in games against Chelsea and Manchester City, some had questioned whether United still had what it takes to win the big games.
Yet at Arsenal they utilised a makeshift defence, and showed a great understanding of van Gaal's 3-4-1-2 system, killing off the game with a superb counter attack. It's taken a while, but United are finally growing under van Gaal, and their first away win of the season shows the progress made.