Following on from the discussion started on the one man tent thread which started to drift wildly off topic, I though I'd share my experience with the Osprey Exos 58 pack. There is also a far better review of it here.
I've had this pack for a couple of years now so think I've given it a pretty good trial. I bought it because it's light weight, has an external frame which gives added comfort and was large enough to pack for both winter and summer overnighters.
The bag has good storage options with five pockets on the outside, two on the hip belt, plus one under the lid and of course the main compartment. This allows you to pack things in just the right place for either security or easy access. I like the way that the pack can be cinched down if you're carrying smaller loads. This aids with stability and means that the pack doesn't flap about on your back.
Inevitably, when a 61 litre pack (this is a 61 litre as it's the long version. The small is 58 litres I believe) with an external frame, weighs as little as this, there are bound to be some compromises and this pack is no exception. The padding in the shoulder straps has been 'drilled' out and is pretty thin. This is no problem as long as you don't try to carry too much weight (the foot spa is definitely out!!). The hip belt doesn't have any padding at all but as the external frame is so good I've never felt this to be a problem. The only rigidity in this pack comes from the external frame, the rest of the fabric is very lightweight although extremely strong so careful packing is important.
I haven't seen many of these about as I've been walking but I really like this pack and I turn to it most of the time, even just for day walks when I could use my OMM pack which is much lighter and smaller but doesn't have the ventilated back, or one of three other heavy weight military type packs or a couple of Berghaus 'day' packs. When I come to think of it, I have got at least nine rucksacks and this one is without doubt my favourite.
In summary, I would not hesitate to have another Osprey pack and I would probably have another Exos 58 if only they'd do away with the dreadful grey and orange colour scheme!!