The 1,200 ci Gregory ISO is a small volume pack designed for short, fast, and light trips. I used this pack mainly for long distance trail running, mountain biking, and day hikes. It certainly meets many requirements a fast-packing day tripper would have; lightweight, lots of pockets for organization and quick access, hydration compatibility, and Gregory's well-known commitment to comfort.
Besides the main compartment, there is a zippered front pocket with three internal divider sleeves, an expandable helmet or "stuff it" pouch, an internal hydration sleeve (with backpanel accessibility), two side panel mesh water bottle pockets, and two zippered, mesh hip belt pockets. Most notable among these, the helmet pouch zippers tight along its sides when not being used, but expands and securely holds a helmet or other bulky objects with ease. Another nice feature is the zippered hydration bladder access on the backpanel that makes refilling the hydration bladder much easier without unloading the pack.
The hip belt pockets can hold a compact digital camera or a couple energy bars. These pockets are easy to unzip one-handed, but the zipper requires two hands to close. This was only a problem while mountain biking; not so much when hiking and running.
Although Gregory’s assortment of pockets are well designed, I personally don’t need so many pockets and internal dividers. Eliminating a few (or most of them) would not decrease functionality for me and the weight reduction would be preferred. Nevertheless, all of the pockets are well designed and easily accessed.