The company line: "We built our new Sweet Pack Vest for anglers willing to go the extra mile (or ten) in search of the sweet spot. This daypack/fishing vest combo is engineered to comfortably carry and organize everything you need on the trail and on the water. Made from tough, highly water resistant 840-denier coated ballistics nylon with a DWR (durable water repellent) finish, the Sweet Pack Vest’s main compartment features multiple fishing-specific interior organizing pockets, exterior lash points on pack and shoulder straps, dual side water bottle pockets and an internal hydration bladder pocket. Up front, the vest maximizes comfort and convenience with lightweight, breathable mesh construction and easy-access vertical pockets. When fishing fast and light—or closer to the car—the vest easily detaches from the pack to be worn alone."
Fly fishing packs and vests are, in my opinion, highly personal and often mission-specific items. This is so much the case that I have yet to own one that I absolutely love. Ultimately, almost all of them do things well, but make sacrifices or have flaws that prevent them from being an effective all-around solution.