The day-to-day value of Bitcoin, and therefore its utility as a proper currency, certainly isn't reliable. For me personally, the time when people can (and do)

The day-to-day value of Bitcoin, and therefore its utility as a proper currency, certainly isn't reliable. For me personally, the time when people can (and do) reliably list prices in BTC (which do not float with BTC/USD exchange rate) is the time when I take Bitcoin's use as a currency seriously.