I think probably the reason people don't have problems with the Chanel bags, is because of their size. It's fine to have a chain strap if the bag is small so you can't stuff a whole lot into it. Therefore the weight would be reasonable.
Judging from the size of this bag, if you're like me and are prone to overstuffing a bag to capacity and beyond, then I wouldn't go for this one because the strap would be painful very quickly.