Well, i think that bitcoins still fullfil some of the requirements and functions as a currency. Bitcoins are also meant as an medium of exchange and several peoples are now going for them which means that they are really spreading more widely. Also a lot of stores are been started which accepts bitcoins as a mean of exchange there and bitcoins flow into the circulation.

Bitcoins too serve as a unit of account untill and unless they are accepted as a mean of exchange. They are not managed by a individual firm or company and it makes them a way diffrrent from the other currencies which still make a better unit of account.

Now moving forward, bitcoins are not a stable store of value due to the heavy fluctuating price and i think that this makes bitcoins a bit different from the sovereign currencies.