I played through the game in one day. Not sure exactly how many hours, but Mentok's 8 sounds about right. Unfortunately, a fair chunk of that was trial and error from dying over and over and over again in the awful combat sequences or wandering aimlessly because the level design doesn't give you much of a hint how to actually get where you need to go. But it was still a solid game.
Unlike Mentok, I actually liked the story; it wasn't great or amazing or anything, but it was decent. I did see the big twist in the final act coming a mile away, but it didn't bother me.
Basically, I think a lot of people are disappointed with the game because it's got a couple of groundbreaking innovations that hint at a lot of potential, but the game itself doesn't reach its full potential--it's only a good game with some annoying flaws instead of the phenomenal new experience everyone was expecting.
Ditto on the soundtrack, though. If one thing in this game does truly excel, it's the beautiful soundtrack. The main theme is especially great, although I prefer the instrumental version to the one with lyrics.