I hate not being able to give a higher rating...
First off let me start by saying I ~loved~ the flash. The story was amazing, the presentation was very well done, the animation was smooth and impressive. The ending was a bit ambiguous, but I loved it.
That said-I think that sound could have added so much to this. "Dun dun da da, dun dun" got very old very fast; to a point it made me bored with the movie. Sound effects, some dialog between the humans, some sounds from the "enemy" could have done wonders for this.