Just finished it. Loved it, especially the story - could become a great series. I really hope they do make a sequel.
Oh and if you get to the credits, keep watching. Edit: or not, you can see that short bit at any time from the main menu.
Here's my summary of this game which I also posted as a user review.
The game is definitely not without faults. Environments are often very narrow, some fights are needlessly restricted/repetitive involving limited AI patterns, and one or two stealth sections are just boring (though once I realized I actually had a crossbow, one was actually pretty decent). But the gunplay is actually quite good, the graphics and sound are fantastic, the atmosphere is great, and the story, dialogue and characters are very much to my liking. Once the game is over, you have a fantastic setup for a second part, and considering the lessons undoubtedly learnt from this difficult first game on a new platform with some of the best graphics ever so far, the potential for the sequel is excellent and I can't wait to dive back into this world and finish what is clearly a larger story than just told in this game. Unfortunately, I fear that will be at least two years, if ever.