Personally I give a solid 8/10. AC IV was a better game; 9/10 for that.
After the consensus about
Black Flag, hearing a 9/10 for that makes me EXTREMELY skeptical on these ratings, haha.
Personally, I just got into the second area recently. I'm at 60% completion, except I did ALL of the extra stuff on the way, including the Artifacts, Ithildan, Outcast missions, and weapon missions. I intend to 100% everything, but Hunting Challenge 7 has been an elusive PitA (was about to kill a Graug, and then it disappeared, pretty awesome...).
Right now, I'd agree with the difficulty assessment. The lack of a real penalty from death is a big reason the game is easy, for starters (I think I've died maybe 8-12 times, not really sure). Like was said, once you get into double-dipping on the combo building and the streak requirement drops from 8 to 5, it gets REALLY easy. Except, for me, what I prefer to do is maybe 1 brand, then a Wraith Flash (I think that's the ground-pound move). That gives you 3 more points on your streak, so 2 hits lets you rinse and repeat that pair of moves.
So, I imagine that this game never gets to challenging you once you're into the second-half of the map. They make it too easy to build up the combo meter (I got it over 100 casually when I was fighting The Hammer), and you have so many moves (which are AWESOME) that it's hard to see where the challenge comes from.
I would probably be on the 8/10 fence, with a lean towards 8.5. I think that the gameplay is phenomenal, and that the story is pretty good. My only knocks come from the lack of difficulty and the also-ran ideas of the Reforge towers (
AC's Leaps of Faith) and the random item pick-ups (like the feathers and flags and crap from
AC2). It really strikes me as
Assassins Creed with a great combat system that makes you want to fight, not just cower and counterattack.