I installed "post rating system" in phpbb 3.0.10 and its working fine.if you are going to implement the same mod you just need to some modifications in the code.
Search it in google,you can get the download link.
PHPBB gives me lot of stuff.everything works awesome.
phpbb is not offering a user to rate each post. user can only post a topic instead of that ,if you provide the mod for evaluate each post.that would be great....