I purchased this vest after first trying the HydraQuiver Single Barrel and finding that I couldn't get it to fit comfortably. The Vest Pack fits me perfectly (5'7", 14.5" neck, 36" chest). The mesh padding isn't quite as plush as on the Single Barrel, and the bottle pouch isn't quite as long and is less rigid, but both work well. The bottle is rugged, with a nice tight bite valve that doesn't leak and allows for a good flow of liquid. The two chest pockets are nice and roomy. I'm carrying two 8 oz. Human 8 Ergo bottles from Ultraspire in these pockets so I can have some electrolyte replacement and fuel in addition to the main water bottle. These bottles are nice and flat and fit the pockets perfectly. The two shoulder pockets are stretchy and surprisingly large when stuffed with gels or energy bars. Easy access with a sturdy velcro strap. The bottle height is also adjustable with a velcro strap so you can use either the included 24 oz bottle or the 21 oz bottle included with the Orange Mud handheld.
Fortunately I haven't needed the included whistle yet. The back pockets are pretty limited capacity, but can hold a very light windproof shell jacket, along with ID or a phone.