Loving it for all it's flaws
The level of freedom is fantastic, I've had it for a while now and the only reason I touch the main story is if I need to to get an upgrade. The assassin management of prior games (where you send them around the world on stabby missions) is replaced by fleet management missions (Battling to open trade routes and ship goods up and down and across the continent(s).)
My biggest gripe with this is that you can't play this aspect of the SINGLE PLAYER game without logging into Ubisoft's servers, and if I'd known that before purchase I might not have bought it on principle.