Bitcoin as unit of account (measure of value) does not exist. Products sold in bitcoin are priced in local conventional currencies and bitcoin price is altered frequently to match the changes in Bitcoin valuations.

Now somebody may say "That's now but wait until Bitcoin takes over the world." That's a another problem. Global currency or fixing exchange rates is not a good idea (Bretton Woods was a failure). There is thing called optimum currency area. Euroarea is in trouble because it misses many criteria for optimum currency area. They are fixing them now. Without global fiscal union, world government and free movement of labour, global currency and single global unit of account is not a good thing.

As a payment system it's already choking and can't easily move value form one person to another. You need intermediaries and intermediaries between intermediaries to fix the system. If you end up using Visa or Mastercard payment system to pay in BTC what's the point?

I think cryptocurrencies and have a place in the future, but Bitcoin is not it.