Great hydration pack with two weaknesses.
Large reservoir volume, good storage organization
No back ventilation, warm.
Perfect volume to stash a rain jacket, tube, pump, tools, small 1st aid kit, food, cell phone, and wallet. It stays close to your back and doesn't move around when descending. The straps are wide and don't chaff, and it carries its weight evenly. There is a tool pocket and an organizing compartment inside, a nice touch for securing tools inside the bag.
I have two complaints: The back panel does not breathe and gets hot and sweaty after long climbs. It holds moisture/sweat and needs to be washed periodically to stay salt-stain free. Secondly, there is no helmet carry feature. So if you use a Bell Super 2R and remove the chinbar for the climbs there isn't anywhere to store it easily. If you ride with a full face on the downs and half-shell on the ups, you are completely out of luck
Overall, a good pack, with two major weaknesses.