It is basically all the negatives of having one electronic payment method (If you lose it, you have no money unless you have cash on hand or can somehow get money out of the bank... if your bank even has a physical branch nearby) with all the negatives of having multiple credit cards (It is a lot more attractive to thieves / skimmers)
With a whole bunch of new negatives like, if you lose your Coin, that means someone has access to all your cards and even if you don't lose it, you are essentially handing people your entire wallet when you use it. Skimmers probably love this thing. Oh, and not to mention: You can't use it online. So all those pesky credit cards; yeah, make sure to keep those around because you still need them.
It just didn't make any sense to me. Pay $100 for no real upsides and a lot of really terrifying downsides.