Bitcoins have three useful qualities in a currency, according to The Economist in January 2015: they are "hard to earn, limited in supply and easy to verify". Economists define money as a store of value, a medium of exchange and a unit of account, and agree that bitcoin has some way to go to meet all these criteria.
Bitcoin can be usefull for the economy if it will adopt totally by one country and allow it to become useful like for online payments and can be use to buy online goods and services freely like how we use our fiat money. Although in my country we already use it to buy loads and pay bills but i think it's not yet enough to say that it was good to the economy. It needs more improvement and development. Maybe after a couple of years,who knows it might happen to become or consider as a secondary to fiat currency.