Freaking awesome
Granted, my review is probably a little slanted since I'm into gory stuff like this, but I loved it.
Great voice acting, great animation. I really couldn't find a single flaw with this flick, including the plot. Even though there wasn't really a concrete conclusion in order, in a more traditional sense, you could still tell that it would end up with both of the rats completely mutilating each other.
A bit childish for some audiences, but everyone else will love it (and judging by the reviews, they DO!)