My point is the following. There is a distinction to be made between units and formats. When I type say, 0.25 in a cell, I can chose the display format to be a number (0.25), a fraction (1/4) or a scientific representation (2.5e-01). What you as a user mean by 0.25 is something else. Does it represent a speed? a weight? heat flow? a probability? In other words Numbers does not care about the units associated with that value.
Except, so it seems, and only in version 4.3, if you choose the format to be currency. In that case, Numbers seems to say, hey, if you divide a dollar by 2, you results should be expressed in dollars. In other words, Numbers is treating the format as a unit.
So, consider the following scenario:
• one cell contains an amount of money to buy, lets say shares, formatted as a currency.
• another cell, which represents the unit cost of each share expressed as a currency.
When calculating how many share your money can buy, version 4.3 of Numbers does both the math and the unit conversion for you and let you format the resulting number as you so which (try it).
Now, you might argue (and I agree with you) that the unit cost is not a currency, i.e. that the units are not $ but $/share. So, since Numbers does not have a way to select "display this as a quantity whose units are $/share", what should I chose amongst Number's display possibilities? Display as currency or simply display as number?
Version, 4.3 makes a strong statement about this while previous version did not.
My preference? don't confuse formats and units and don't try to be too clever.
Just sayin'
Hope this helps.