I do a lot of around the legs, so I can definitely say that playing diabolo helps build your arm muscles exponentially.
Pulling the opposite sex
I heard a couple of years ago that juggling (and i suppose diabolo) can help with: ADHDdysgraphiacoordinationSelf esteem/confidenceStress (its relaxing)It teaches concentration, patience, timing, tracking skills, gross and fine motor skillsAs well as the social and creative elements of diabolo (like guppygould said).