I have just bought one of these from Warehouse Express for the princely sum of £59.00 plus delivery.
I was a little unsure as to how it would be but was pleasantly surprised at the build quality a well made bag and comfortable to wear.
The bag has a spring steel frame keeping a gap between the carrier and the bag helping air circulation and keeping my back dry.
I easily managed to get all my stuff in the bag it has a compartmented btm section where I got my 20D plus 4 lenses and other bits, in the front external pocket I put 3 batteries and 3 memory cards.
The top section has plenty of space for sandwiches waterproof woolly hat gloves and 0.5L flask.
There are 2 side pockets in one I got my 100mm filter holder and filters leaving the other for easy access stuff. there is also a built in tripod carrier and it is supplied with a rain cover. the straps are substantial and comfortable and adjustable to take a fat bloke.
There is also a side accessed compartment for a laptop but I use it for my OS maps.
You can also attach it to a trolley in case you decide to really fill it. 🙂
UPDATE 18th October 2012
Well I have had the bag a fair while now 31 months and I use it all the time and its as good as new still if I find another I will grab it and that should then last me out.
UPDATE 22nd January 2014
Managed to buy another K3L from a seller on Ebay the bag is like new , I am still using my original this one is a just in case one as the K3L is no longer in production.