Hmm. To date I either where a jacket or armor when I ride, so I have never really considered the vest. Backpacks have generally worked pretty well for me if I have to take more than just a few items. That vest on Amazon is pretty pricey! I mean you could get a nice backpack with a Camelbak in it for significantly cheaper than the cost of that vest I would think?
Also, I do have a little bag I strap to the Manracks rack on my TW, and that works for most things. So between that and my jacket pockets, I have seen no need for something like a vest. If I am going on a longer ride I am strapping things to the back regardless.
Good luck making your decision.