In reply to BarmyAlex118:
Can't speak highly enough of the Crux range. I have the ak57 (comes in other sizes) and it holds enough for nearly a week's mountaineering (with tent/bivi) while only weighing 1.1kg. Light or what? And they don't sacrifice strength as its made from thick kevlar. Its also reasonably waterproof.
It's very minimalist but despite this I have found it very comfortable... more so than many aussie backpacker specials. The compression straps zigs back and forth three times (on that model) so compresses very well with no bulges.
BUT don't expect any fancy frill such as extra pockets (it has a lid pocket only so it takes a while to learn how to pack it well), cup holders, bottom entry or all those other things. Though it does have have a platypus pouch. It's VERY minimalist! It also looks pretty dull if that sort of thing matters.