I recently bought an Osprey hydration pack. The Raptor 6. So far I only have one ride with it, but I am very impressed. First off, it fits great. I had about 50 ozs. of water, multi tool, co2 and phone, and it felt very light. The bladder is Nalgene and has a rigid spine to it. I rode for an hour and a half in 100 deg. heat and the water stayed nice and cool the whole time. The bite valve seems to work well, and the magnetic clip is a really nice feature.
All in all, after the first ride, I would have to give it 5 out of 5 stars. I'll update my review after more riding. In the mean time, if you are in the market for a new Hydration pack, you should consider the Osprey.