Ive been using them for a lot of years, and for hot weather, with unreliable water sources, I use a 3 liter plus two water bottles. I don't take it out in cold weather though, or where I know there are frequent water sources. For me, the value lies in the large capacity, and the versatility of using it as a pillow, camp water bag, improvised shower, etc. (all tricks I learned in Iraq and Afghanistan where the military has pretty much stopped even using canteens, just issue generic camelbaks.) I don't really like the weight on my back on a bike, and when I can fit it I usually lash it to the rack and just use it for water storage.