Not your run-of-the-mill MMO.
The world and the environment: I haven't moved on to the later zones (still in the first 3 zones), but it looks like Silent Hill. It has the best environment and world of any MMO.
Questing is fun. Questing always is the biggest time sink in any MMO and this is where the game shines. The story is brilliant.
The voice acting is better than any MMO (including SWTOR), although they all seem a bit over stylized. The movement and gestures are unique while the NPCs talk. I wish my character could speak though.
Also, finishing one zone is not a quick process, there is a ton of content.
The huge number of abilities available to any character makes tinkering with your build fun.
Combat, PvP and dungeons are just as good as other MMOs (these apparently are not the focus of their innovation, but they are good nonetheless).