I haven't used this yet but I am going to in 3 weeks when I go to Vietnam.  I have examined it (it is made well) and tried it on (36" waist no problems)
I don't fear pick-pockets over there but more my spacing out and leaving something unattended.  I figure if I have most of my valuable papers and money strapped around my waist I'm less likely to leave it on a table or a hotel room or a bathroom sink.