I'm neutral. I will usually do good deeds, but eventually I end up doing some seriously evil shit. Case in point: my massacre of the family and Arefu (all over the accidental theft of a harmonica, talk about pointless bloodshed) and my aid for the ghouls in the conquering of Tenpenny Towers. That character was neutral at level 8, very good at level 12, very evil at level 20, and back to neutral at level 30.
Its mainly because I generally don't act like a dick but occasionally take the evil option for big choices (or go on a killing spree).