I agree. With a tail wind the effective wind speed would be the difference between your speed and the wind speed; with a head wind it would be the sum of your speed and the wind speed and with a cross wind it would be the resultant wind speed which could be calculated using trigonometry.

In addition the published wind chill temperature actually only applies to exposed human skin. Assuming that when the temperature is cold enough to worry about wind chill, most if not all of your skin is not exposed, the wind chill temperature would be different from the published value.