I recently purchased the Osprey Daylite rucksack both as a stand-alone day pack and also as it has been designed as an add-on to my Osprey Ariel 65 pack. The first thing you notice about this great little pack is its weight - just 1lb ! However, it is not flimsy, but well-constructed and sturdy enough to carry everything you'd need for a day's hiking or as a commuter bag. As usual with Osprey it has lots of useful features such as the adjustable sternum straps (which also adjust up and down on the cleverly designed sliders and include a whistle on the clip as with other Osprey packs), waist strap, compression straps at the sides, mesh side pockets, a large main compartment which has a vertical divider to keep your stuff separated, a half-depth front pocket with kep clip and divided mesh pocket, and hydration pack sleeve in the back for easy access for refilling.
Although small and light, this pack can certainly hold plenty and it doubles as an add-on for certain Osprey packs to give an additional 13l of capacity.
All-in-all an excellent multi-use pack at an incredibly good price.