The only problem I can see with it is the limited capacity, as others have mentioned. The strap setup, at least on his pack, also doesn't look very supportive. I would imagine that one shoulder bearing the majority of the weight would get quite tired after a while. I suppose with a pack that small it wouldn't weigh a whole lot though.
im still using my military belt ,suspenders and fanny pack set up,hes using a army pancho only problem you get soaked from the knees down,you can hide a small carbine and pistol under it ready to use with out being seen,