It's his personality which is the key imo.
He has made very few mistakes but he still gets his first touch wrong sometimes or lets a ball bounce when he shouldn't etc, but rather than do something desperate to rectify it, like Mangala would (or Stones himself would often do last season) he mainly chooses the best option to repair it.
That's what has impressed me most about him. It's not the kind of genius some suggest, to knock a ball 20 yards, it's having the right mental approach to get it right without fucking it up. Mangala 'could' do it, but he won't. That's not because he can't control a football or pass it, it's because of what's going on in his head at that moment imo.
Stones is already talking up Aguero & asking why he's not been voted poty. He feels as if he belongs here & is talking as if he's been around for years.
Really impressed me.
I would add though, I don't think I'd be praising him in this way if we had, let's say 'another' manager right now. I recon that would have been one hell of a test.
Pep is very very special & is doing wonders for Stones & others.