The clever part of the design of the 3N1-30 is in the placement of the straps and the position of the zips for the main compartment. The shoulder straps can be unclipped and re-connected either as the twin straps of a rucksack, or by connecting the strap to the clip on the opposite corner it can be worn slung across one shoulder, with the unused strap tucked away behind the back padding. In this position it is easy to swing the back round in front of you, where the side-opening of the main compartment gives quick access to your camera. The compartment opens on both sides, and the internal partitions can be re-arranged for either left or right-handed operation.
The bag can also be worn with both shoulder straps crossed across the chest, which gives the load support of the rucksack configuration, but allows it to be swung around front by simply unclipping one of the straps.
While the swing-around design isn't unique – the Lowepro Slingshot range uses a similar design – the Kata 3N1-30 combines the convenience of this system with the practicality of a well-made rucksack. At £100 it is quite expensive for its size, but since you're effectively getting two bags in one that makes them £50 each, sort of. Sorry, it must be the painkillers.
My only real criticism of the design of the 3N1-30 is that like many current camera rucksacks it has no straps to carry a tripod. Since like most serious photographers I seldom go anywhere without one, this is a bit of a handicap. There is a large D-ring sewn into the front of the bag, but this is mostly cosmetic. I suppose you could tie a tripod onto it, but it would be quite awkward to carry. However the rather nondescript external appearance does have one big advantage; it doesn't immediately scream “I'm a camera bag full of expensive gear! Please steal me!” to every opportunist thief in the area.
The Kata 3N1-30 is a well-made, stylish and cleverly designed bag that is ideal for both keen hobbyist and professional photographers. It has room enough for a large DSLR kit plus other travel items, and its dual-purpose strap system makes it eminently practical for both daily and travel use. If only it had some sort of fastening for a tripod it would be pretty much perfect.