Old joke is old, I know. Actual picture found here.
Trolls (or as I like to call them 'the simplest monster that will not die from stabbing alone' have 6 giant RHD, but they partially make up for it with Large size and some nice physical ability scores. They can also use weapons and armor, which sadly means they must give up their claws and Rend. Mental stats aren't great either, but let's face it: nobody becomes a troll to be good at spellcasting.
Most importantly, however, is Regeneration, which is undoubtedly a very strong ability. While it doesn't render trolls quite unkillable, it will do wonders for their survivability and means that some (mostly unintelligent and unknowledgeable) foes won't be able to kill you at all.
The mix of RHD and good traits leads me to assign a +0 here.
It's a viable alternative in aquatic campaigns, where a swim speed and ability to breathe water will come in handy and your regeneration restriction doesn't apply that often. +0 here as well.