There are lots of exchanges not only xapo that shoulder the transaction fee. And indeed this is not news at all. Even some gambling site shoulder the transaction fee which I can name, FortuneJack, as one of them. With the free transaction fee came the risk because in Xapo you are not holding the private key to your Bitcoin address, same with other online wallet out there.
That is true. I use Xapo and although so far I had no issues and problems there is a risk because of the private key that you don't hold. Seems that fees are quite an issue lately and I don't know how this will be solved. But I know we have the choice. You can use suggested fees and everything will go fine or you can take risk with very low fees.