The online payments with cryptocurrencies are already a reality such as OpenBazar. However, not all of us have used Bitcoins for buying something material.
So in this sense, the question in the title is a fascinating one. A question of which I already gave my answer on Quora. Here you find it https://www.quora.com/Have-you-ever-bought-something-with-Bitcoin/answer/Alket-Cecaj?srid=n9bS
There is also an incoming ICO of UTRUST that should make it possible for people to pay online and offline using cryptocurrencies. You can find more here https://utrust.io/ico