I use this vest for longer runs in the 13-20 mile range. The design is really simple and straightforward, foregoing most of the bells and whistles of a Salomon ADV Skin Set Vest, which I like to use if I need more organization/storage options for long runs or ultra races.
The pockets up front hold gels, phone, soft flask bottles, but the layout is simple and minimal, which isn't necessarily a bad thing. The main pocket is spacious and has room for extra layers and a bladder with a smaller zippered pocket to hold keys/sunscreen. The mesh pocket in back can keep your ultra light Houdini-like shell easily accessed or allow it to dry out if a shower passes without throwing it in the main compartment. The additional feature of the trekking pole holders in the back are solid and straightforward to use which is much appreciated.
The performance of the vest is really secure and resistant to bouncing or movement while running or scrambling. The adjustable front strap system is great for different body types and allows a more custom fit than traditional vests. This thing just sits really comfortable and stretches and conforms to fit your torso well. I wore a Medium - the same as my shirt size and it fits great.
Overall a simple, functional, and straightforward piece of gear, the likes you would come to expect from Patagonia. In fact, it is a pretty logical progression in the Patagonia Trail Running Pack story, coming from the Nine Trails 15L Running Pack and the Fore Runner Vest. If you need more storage, organization, or complication, there are plenty of other options out there.