I've been using this for about six months and love it. I take it on any run over four miles in the summer; even with the water reservoir and the pouches full you barely feel it on your back. I run with my wife, and it holds enough water for the both of us for runs up to ten miles. The chest and waist belt adjust easily during the run, and the external side pockets are perfect for stashing gel-packs. The zipper pouch is large enough for keys, cell-phone, cash, etc., though if we want to run out to eat, I can even cram in a wicking towel, a t-shirt, and a fresh pair of socks! In the fall when water isn't as big a deal, I've even taken out the water bag and taken along two paper-backs for a day in the park.