In reply to olliehales:
I would second (third?) the Talon 33.
I bought one this year for hill walking / scrambling etc. It's very lightweight, has really useful hip pockets so I can eat on the move and the external hydration pocket down the back is really useful as you can whip the bladder out and refill without the usual faff. The back length adjusts too which is a nice feature.
The mesh pockets are easy to access and it's handy to shove a shopping Goretex into the big mesh pocket rather than back in the pack.
It is pretty thin fabric so I am being careful with it (wouldn't lob a rack in it routinely or thrutch up chimneys wearing it) but that's a pay off I'm prepared to accept as it is so light on the back.
My only criticism is that the top pocket is so volumous (a feature that I like on the whole) when the pack is not fully packed the lid tends to hang down.
Not sure I could pack everything for multiday camps in it without some serious thought mind.
I did the WHW this summer and packed kit and six day's food into a 48 litre pack, another Osprey: the Exos 48. It was the positive experiences of using the features of the Exos that convinced me to buy the Talon.