I finished the game last night. Yes it is very short but it's excellent, there's no padding and its very impactful, emotionally. I got chills multiple times and I'm not going to lie, my eyes misted up a little at the end.
I definitely plan on playing it again, at least one more time to show it to my wife and pick up some more achievements (you only get them for doing weird out of the way stuff). It's kind of amazing no one's tried controlling two different people at the same time before, in my recollection anyway.
I loved the Fable-esque atmosphere, the music was great and I think the nonsense language made the game stronger and more universal than if they'd gone with English.
$15 may seem a lot for a game that's only a few hours long but it's on par with the price of going to a movie, in this case a really good movie. I recommend it heartily, now and when it comes to other platforms. I bet on the PC it'll look amazing.