You know, I've always assumed the “job” part of a blowjob involved stuffing something in your mouth, not the physical manipulation of the penis. “Hey, baby, I know that it might get uncomfortable holding your mouth open for long stretches of time. But why don't we try cramming something else in there along with my cock and see if it doesn't feel better?” Unless the vibrating bullet adds enough to the BJ to cut the time in half, I wouldn't imagine it would be worth it to the giver, but I really can't imagine that it could compensate for the visual of the woman with a mouth guard in. Maybe that really where it saves the work — guy sees girl with blowguard, guy loses erection, girl doesn't have to do bj.