Finished it yesterday, or at least the main story and the killing off the Order questline. I don't feel like finishing the modern day or Odin stuff.
Overall I liked it enough that I think it was worth the money, but boy did it get to be a drag by the end. Too long, too repetitive. I wanted to see where it was going, yet I hated the process of getting there for the last couple of hours. If there was anything else to play right now I probably would have stopped playing and just watched the ending on youtube.
Also, I found the difficulty curve near the end got pretty easy. As you get more health packs and arrows and better armor, your real power level is a lot higher than what your skill points would suggest. I finished at level 300ish, but I had 0 problems taking out the last few missions where guys were supposedly 340 or higher, including the zealots. Whick honestly is a good thing, because I certainly wasn't going to grind out another 40 levels just to see the end of the story.