Exactly what tricky parts have I ignored? I don't think I've ignored the tricky parts at all. I've presented them in a working context that makes them seem less tricky in the first place.

There is no denying the appeal of a metric system where each unit is an order of magnitude different from its neighbor, but when it comes to cooking, the old system's units tend to be easier because you can use 1 tablespoon instead of 15 mL, or 1 cup instead of 237 mL. So there's a practical advantage because the units are sized for household work. A milliliter is too small a unit for cooking. A liter is too big. Do you want to measure out 2.37 deciliters of milk or one cup?