Never done it.
I'd consider doing a little trim, but not a full shave. The surface ain't exactly smooth like a face. On the other hand, my nuts receive compliments the way they are, so I'd be scared of jinxing that
As for shaving your ass, I'd be scared of two things: 1) cutting myself and being scared to death every time I crap and 2) itchyness as the hair grows back
Man, I have no idea how women do all this shit...