Can you expand on;
"but no one has had to pay the price until they start using the newer processors."
Since M0 doesn't have FPU, any floating point math will require all SW which will affect performance. However, if you compare an AVR chip to M0, the M0 will still be vastly faster (and enough storage to hold the extra data) than the AVR processor. Still, if you compare the software calculation speed using floats vs doubles on the same processor & clock, the float calculations should, realistically, be 2-3X+ faster.
However, my comment was more factored by libraries, like DS18B20, returning doubles....