Been using a HAWG NV for a few months now.
I cut off the flouro yellow rain cover. Gives me an extra pocket and saves a few grammes.
Firstly, for me,very comfy. Have carried bike kit, shopping, work uniforms, spare lights, wallet, keys, money, mp3 player, lock. Great. Seems small but it swallows gear and everything fits in. 3l bladder fits into an insulated section. Has kept fluids cool even in 40c Ozzie heat. As well as the 3l bladder there's 18l of space.
Off the bike, take off the lumbar straps, remove the NV back panel it's great bag for day trips – plenty of space for all sorts – food, camera etc etc.
Basically, can carry lots of kit, comfortably, or just a bit of kit with straps cinched up tight.
Niggle: The straps that cinch up to tighten the bag seems to be in a really silly place. Once the straps are tight it makes it awkward to get into the 2 side pockets, or into the main compartments – can't help thinking they could be better placed.
Hope this helps a bit!