I got to play a good amount over the weekend (8 hrs or so) and I have to say I think the game is fantastic. I'm really, really enjoying it.
The story is intriguing and interesting. I find myself actually slowing down and reading/listening to NPC dialogue to understand what's going on in the world.
The atmosphere, artwork, graphics, character detail, etc. are beautifully done. They have a gritty realism about them that I rarely find in games today. For me it harkens back to what Diablo 1 made me feel like when it comes to atmosphere, character detail, artwork, graphics, etc. It's all immersive and sucks you in. IMO, when it came out, I was hoping Diablo 3 would have the same level of the aforementioned attributes but it ended up looking and feeling more World of Warcraft which was very disappointing to me.
The Combat is very well done as well. It is tactically satisfying and more often than not definitely a challenge. I find myself really having to study the environment i'm in, what my party's strengths/weaknesses are, and know the intel on the enemy. If you just rush in, you're going to be at best mauled pretty badly, or flat out creamed entirely and everyone killed.
I like how you don't get experience for killing monsters but by completing quests, discovering new locations, doing things like picking locks, etc. It's better than " go kill 20 moglocks for X amount of XP" type deal.
The music is great and really well done. It supplements the atmosphere very well.
Try as I might, and I am as objectively as possible, I'm really struggling to come up with negative feedback or criticism on this game. It's wonderful and really a great addition to the old Infinity Engine games of the late 90s. I think it'll end up being one of the top games in 2015.