We're working out what we think - we'll add our view here!
Gossamer Gear says:
A hiking fanny pack to wear as a backpack system or alone on small adventures now with more volume.
The Hipster Fanny Pack is an alternative solution to hipbelt pockets with the advantage of staying on waist, even when you drop your pack. It sits tight against you and is completely hands and worry free! Use it to carry items you want quick and easy access to during the day like your compass, water treatment, sunscreen, etc. We like to put it on first before the pack, then lay the pouch of the fanny pack over our ultralight packs with a hipbelt. Waist fits Men, Women and Kids for everyday adventures!
We're working out what we think about Gossamer Gear's Hipster, we'll add our comments here in due course.