My wife has one, and is quite happy with it. She has two of the large bottles in it, leaving plenty of room for other stuff (usually a camera, light jacket, some snacks, that sort of junk).
I have the old model HAWG which is just big enough to carry a 100oz bladder and a change of clothes. I use it a lot for shooting classes and a general utility bag, but wouldn't mind just a tad bit more space. This year's new larger HAWG is worth looking into. I'll have to order a demo and see for myself.
BTW, we offer 25% off all Blackhawk and CamelBak products to TFL members, or you can contact BH directly if you like.
I have been using Camelbak products since 1994. I bought a M.U.L.E after I used a friends' Camelbak with a Packster cover for a mountain bike ride by the lower Salt River. I also used it for day hikes and summit assaults. I bought a H.A.W.G. from R.E.I. about six months ago. I love it. It will hold my EMT textbook, 100oz of water and a fistfull of PowerBars (it will also hold a Balistic Conflict Resolution Device without printing, not that I would take one to a school) when I RollerBlade, or bike, to class (about eight miles from home) or work or where ever else I might go. It is very handy for the range as it will hold enough food and water for an entire day of shooting, or until the ammo is gone (never enough of that stuff!). I also use the 100oz bladders in my MountainSmith pack. If you don't have one yet, get one and then wonder how you managed without one for this long.
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Guns cause crime like spoons cause Rosie O'Donnell to be fat!