It is a unique auto axe that deals much more damage than the original. It has a larger damage/hit and damage/second ratio compared to the standard auto axe (45 compared to 35) and uses less AP (50 compared to 65).
Though The Mauler is the single most damaging melee weapon (with the exception of the Shishkebab with the Pyromaniac perk), it is also the heaviest, making it a more difficult weapon to carry around.
As this weapon hits exceptionally fast for a melee weapon, using the perks Superior Defender and Ghoul Ecology can lead The Mauler to a much greater DPS stat, far surpassing that of any non-automatic melee weapon.
Grinding barrels and other physics objects will usually result in damage, as they will be pulled violently into the player, then spat off in some random direction at a decent rate of speed proportional to the mass of the object: cars will sometimes scoot towards you, barrels will hit a player hard enough to damage, and shopping carts rocket off like bats out of hell. It is possible to kill non-player characters with lots of patience and no repercussions, by repeatedly flinging barrels at them with The Mauler.
The following is based on unverified behind the scenes information and has not been confirmed by canon sources.
The fact that Everett mentions Monroeville, PA and chopping up ghouls with it is likely a reference to the fact that the Monroeville Mall was the location where the original Dawn of the Dead was filmed and in Night of the Living Dead the police and news casters call the zombies "ghouls". Also, "zombies" is a common derogatory name for ghouls.
ps3pc When using it in first person mode, it may disappear mid-animation. Bringing up the Pip-Boy immediately afterwards you will notice that your Pip-Boy has disappeared too (but not the screen). Changing to a different weapon quickly clears this bug. [verified]