I had my doubts initially - most of it due to ensuring a proper fit like others who have negative reviews. Give it some time to make minor adjustments, though, and you'll never head to water without it.
Main Pocket: The thing looks small, but is a modified day pack - keeping the bulk over your back and out of the way (and water) to provide the freedom to cast, retrieve, fight, and land fish. I can go all day with it on, meanwhile holding 2-3 fly boxes, Steripen (water purification), a day's worth of snacks, compartment for your shades, sun screen, Ultrathon bug repellent, and a 32 oz Nalgene (seen at the bottom). The phone pocket is too small for an iPhone 6+ but should be fine for just about any smaller phone. There's a loop at the top where you can stick a magnetic net release to make for easy landing (pictured is the small, Wetfly Catch & Release net).
Tying Table (outside of the main pocket): Changing flies out is pretty slick too. All you need to do is unbuckle the bottom strap and flip the sling around. Then open the tying table compartment where there's plenty of storage space for tippet, strike indicators, weights, nippers, etc. Within the tying table is a foam pad to dry out used flies.
Along the Strap: There's a small compartment that'll hold small things such as chapstick, cigar, or gum and has loops on the outside to secure forceps and other fishing tools to keep handy while fishing.
Patagonia thought about it all with this one!