I'm an avid, veteran mountain biker and recently discovered road cycling. I own this pack, as well as an osprey raptor 18 and a camelbak luxe (not sure of model name -- won it in a race). I highly recommend this pack, for the following reasons:
1) the aircomfort flex light system is a winner. Both the osprey and the camelbak are sweat sponges and they make me too hot. after a few multi-hour rides, the osprey and camelbak get disgustingly funky. Not the deuter.
2) while the quality of the osprey zippers and fabrics are excellent, the camelbak is cheesy. The deuter is right up there with the osprey.
3) the deuter reservoir, bite valve, and hose:reservoir connector are markedly superior. The osprey is a close second and the camelbak is embarrassingly bad by comparison. I like the magnet that keeps the osprey's bite valve close to your mouth, but the absence of this feature on the deuter isn't a big flaw.
4) the deuter's helmet attachment is simpler and more flexible than the osprey's, accommodating either a full-face or an xc race helmet. No chance of getting a full-face onto the osprey.
I can fit knee and elbow pads, tube and patch kit, first aid kit and gopro in the deuter with a full water reservoir without expanding its capacity via the clever zip-to-expand feature. Or, when I do my 45 mile road bike commute, it easily fits MacBook Air 11" in the hydration sleeve, clothes, and dob kit. After those rides when the pack sits next to my desk at work, I especially appreciate that it doesn't sponge up all my sweat like the osprey and camelbak do.
I owned a previous deuter hydration pack for 12 years and sold it to upgrade to this for expandable capacity. It was rock solid reliable and this one has been too. Give this pack a close look. I am clearly a big fan.