Strictly speaking, it is not Gresham's Law, rather an extension to it taking into account a floating exchange rate between the currency pairs that I proposed somewhere in this forum...
Yeah I just read about that to clarify.
But it does not make sense to spend BTC if people accept (ostensibly inferior) USD--presuming
the exchange rate is fairIf the exchange rate was fair and only that was counted in, then your assumption wouldn't be reasonable (in fact, it would be false just because of that alone). It is individuals expectations about future exchange rate that make Gresham's Law valid even for floating exchange rates. I edited my previous post giving the link to the discussion about it. So if you are interested you could go there and read my explanation (ant its critique) why Gresham's Law still holds...