Somehow, the overall "mood" of the sky doesn't seem to match what I see in the reflection.
That, and the fact that the fallen tree keeps drawing my eye, making itself the "subject" of the photo--but since it's not a very compelling subject (to me anyway), it just doesn't quite do anything for me.
EDIT: I think the reason for my perceived mismatch between the sky and the reflection is that the sky has that little bit of blue off to the left. I realize that it's completely plausible the blue was just not where it would have been reflected, it's just that it creates this "disconnect" in my brain that says something's not quite right.