I think the issue will be that actual results may not reflect the progress we have made, because we haven't got everyone in that we need, and are probably going to depend on younger players as backup to see out games / cover for injuries. There is also the issue around how Ronaldo behaves / leaks to the press.
Pro's
Faster flowing possession football - thank god we finally have a coach that balances physical effort with touch and technique. He's willing to play younger players in positions that traditionally we have favoured physical cart horses. I'm hoping we see more of Iqbal than we do of "Dray" McTominay
Scrutiny of performances - EtH and his team seem to be able to quickly spot the difference between "trying" to run / press and actually doing it. In th past we had players doing "just enough" running to claim they were pressing / running back, but not actually doing it at full "maximum effort" as EtH is often heard shouting!
Discipline & Authority - Some players did'nt even bother to pretend to put in a fake effort at times last season (Jogba). EtH has been ruthless in getting rid of such players, or is looking to move on players that haven't got the touch, technique or effort to represent the club. He's got rid of the low hanging fruit in Telles and AWB, but will face a sterner test if the Ronaldo situation goes viral in the papers.
Con's
Weak in depth - without going into voodoo economics of Barca it was impossible to cover every weak area in the squad. Ideally we'd want Prime talent in all spots with a mix of talented youth and competent backup as their ready replacements. We're probably going to depend on younger players a little too much this season, with all the inconsistency and errors that come along with that. So we may well dominate a game for 60-70 minutes but then fade as younger playees tire or lose concentration. We will lose games in patches as we get injuries to key people.
Lack of preparation - EtH is famed for his attention to detail and prep work. It's not ideal that we are still waiting for the midfield metronome of FdJ to join us so we can get the right pacing of our midfield and get them interacting with how our forwards will be positioning / running. The Ronaldo situation also emphasises this. I can see a use for him as an impact sub after 60 mins to either smash home some goals against weaker teams or crack open a tired defence with his reputation making opposition defenders panic or change things to try and deal with him. However it remains to be seen if he is willing to accept that role.
Media / fan influence - United is always a big story - add CR7 to the mix and you have a potentially explosive story landing any day of the weak if CR7 wants to leak it. if he remains and becomes disaffected, or other fringe players revert to type and start moaning to the press then I can see EtH might begin to struggle with the role. He is clearly a detail guy, but doesn't maybe have experience of the sort of media onslaught he could face. I think the key here is that fans try and look at output on the pitch, initially probably just for spells in a game, and try not to react to actual final results. I can see some defeats happening, given the weaknesses we have, but if I see progressive play...improving players...growing influence in games then I can accept a few results going against us. The question is will other fans spot this or will they just follow the howls of the sports media and their cliches about "premier league proven" etc.
So the real question is...will the fans and the club continue to back him in the face of maybe a bad start or poor run of results? - i know I will, from what I've seen so far this guys a potentially Great Manager!