I'll rate 5 stars once I can load the game up without my character being drunk and the quest bugs are handled.
Four stars in spite of the bugs, I have enjoyed this game immensely for over 40 hours, and I believe the biggest thing holding it back is Ubisoft's adherence to the old Assassin's Creed games.
The skill system will be good- once they implement a way to save skill presets so it doesn't take 20 minutes to reallocate your skills to stealth, then reset them back to combat for bosses etc. Even with bugs this is my biggest complaint and I don't understand how this wasn't implemented in the playtest stage? It was the first, last, and biggest complaint from everyone with whom I spoke to about the game.
Approach with an open mind- if it's not AC and it's a great game, but as an AC game it's terrible...? Well, then play it as a non-AC game and let it go. It's time AC died its glorious death to let Ubisoft explore the RPG scene fully, as those games are far more fun to develop, play, and have greater shelf lives.
TL;DR : 9/10 once patches are out and bugs stop appearing, even if infrequent it's jarring and a worrisome trend for ALL videogame developers. Great story, fun gameplay, play it like it's not an AC game and you'll have a great time.
Ubi: Polish, polish, polish to a shine and us gamers will throw our money at you. Bet.