Well... it can have its upsides... but it doesn't come without its downsides as well.
It's a disorder called "Congenital Analgesia" (which I often call CITP, for the abbreviated "Congenital Insensitivity to Pain) and it effects my Neuro-system. Basically I have no sensation, reaction or response when inflicted with pain.
In life, it's more inconvenient than it is useful. What purple said is true, if I were to have a severely infected wound (especially on the inside of me), I wouldn't notice it. At most, I would feel a little strange. It's also the reason the Cancer I had a few years back now got so life-threatening. It only came to be noticed when my breathing patterns became noticably unusual.
So yeah... me and my amazing body. 😛