I'm in the 'Let Down' camp
My god the city is bland when you compare it to GTA 4/5 or Saint's Row. I keep forgetting which city it's supposed to be, only remembering when I pass a newsstand with Chicago or Seattle or whatever emblazoned on. You also get too much stuff straight off the bat. Within 1 or 2 missions I had a silenced pistol, multiple Assault Rifles and Shotguns. Ubisoft should have held some of this back to nudge me into the hacking side of things, with such a massive arsenal already at my disposal I didn't see the point in hacking once I got into a fight.
The biggest issue though is that I'm struggling to care about Aiden Pearce: he's got a half-decent backstory where he's out for revenge for his dead nephew, but he is also a bland amoral dickhead who by his own admission only prevents crimes as a 'distraction.' Ubisoft still have not got the hang of compelling protagonists, Aiden is much more Connor/Desmond than Ezio.