I had heard while reading a postmortem that the developers were trying to fix one of the criticisms of the second game of a big world with nothing to do, but ironically enough ended up doing the same thing, maybe even worse. I think from a storytelling standpoint, the game is fine and the cutscenes well done. The gameplay however, feels like a throwback to early Ubisoft openworld games like the first Assassin's Creed; A lot of repetitive random tasks to do before unlocking the next sector, etc. What it tasks you in doing via the storyline might sound different, but they're merely skinned to sound different while you're going through the same motions, rinse and repeat. So, in the end it has this disjointed feel of 'why am I doing this?"
In terms of story, I loved what they were doing and there were hints of brilliance hidden in there somewhere. Seeing Vito Scaletta again was a highlight, and I loved the interaction between the other lieutenants, but man, I wish they had done so much more with what they had. The gameplay systems relating to that all felt severely lacking. On the whole, I'm glad I played it, but still feel like I wanted more out of it.
Spoiler: