Robin2: I meant to be emphatic rather than insulting, my apologies if you took it that way.
And I should have been clearer that your post is correct for some specific (very low power) steppers. I meant that it's a bad approach if taken as a generalisation for all stepper motors, e.g. where you might have a rated current of 3A, about 0.5R winding resistance and want to drive the stepper with about 48V. Clearly those numbers don't add up if you just think of the stepper as a resistor.