Plot: Nothing fancy but not terrible 4/10
Side quests & exploration: Lots of things to do and a large map to explore, but most side quests are short and variations on a few basic themes 6/10
Game mechanics: Very similar to other games from Ubisoft like Far Cry or Assassin's Creed, just with a bit more of an emphasis on gathering and crafting 7/10
Graphics: Probably the best I've ever seen in a video game 10/10
Music: Soundtrack is quite good IMO but for some odd reason there are long stretches when the music doesn't play at all; I finally just turned off in-game music, opened up the soundtrack on YouTube, and had that play in the background 8/10
There are also the usual new game glitches that I expect will be ironed out sooner or later.
Overall: If you'll only be happy with a complex Baldur's Gate level plot or a game with innovative combat and mechanics, then you'll be disappointed. If you're happy to play yet another Far Cry or Assassin's Creed type game with stunningly gorgeous scenery and a large beautiful world to explore and enjoy, then this is a really wonderful game. If you like a kind of laid back relaxing approach with lots of exploration and some crafting and combat here and there to spice things up, then this might be one of the best games I know of for that. I'm definitely in that last category, so my overall ranking would be 9/10.
Favorite in game activity: Start flying somewhere at a leisurely pace and just watch the scenery go by