For me it was a solid 8/10. I thought the premise, art and design, characters, dialogue and base mechanics/skillset all very compelling. The story is somewhat hackneyed, but I can live with that. The Outsider was interesting as a non-judgemental deity (which is somewhat unusual) but his visual design was terrible.
The game becomes less linear as you plough runes into the skill-tree, but inversely, the final few levels become more linear as the game progresses, which is a shame. Also the low/high chaos, lethal/non-lethal approaches to mission objectives, were a bit too binary for me. Fix those in a sequel or better yet, a 6-8 hour DLC and a 9 or 10/10 beckons.