I was really disappointed with the Cath Kidston changing rucksack I ordered. It was small, the material didn't seem like it would wear well and it just didn't have enough pockets/sections. It went back. I think a normal CK rucksack would have been more practical teamed with a washable changing mat (IKEA) and some waterproof bags for nappy stuff and mucky clothes. I just opted for a super practical but not at all glamorous walking rucksack from Osprey in the end.
I use a regular rucksack with a foldable changing mat. So much easier than having a shoulder bag falling off all the time, or swinging down and hitting 3yo in the head. I agree with oneday that the CK changing rucksacks are tiny. The changing mat isn't waterproof and the bottle pouch isn't thermal.