User Review: Osprey Hydraform 3 Liter Reservoir
Source: bought it new
Price Paid: ~$26
Good quality reservoir, good rigid design.
I've got two of these for two different packs. They're hard to beat with the rigid backbone design, maintaining shape as they are emptied, and slipping easily in and out of the hydration pocket. The price is pretty good also, not unreasonable when compared to other big names.
I replaced the Nalgene bite valve with a Nalgene quick-disconnect bite valve, allowing me to fill the bladder from the suction hose using the existing quick-connect parts that came with the Katadyn Hiker Pro.
This bladder is probably a few ounces heavier than other bladders without a backbone, but I'm willing to carry the extra weigh for the convenience this one offers.