As a relative newbie, I think Jellycopter's comment re the accuracy of the ASI when the wind is off the centre line of the pitot is very relevant. Although we are all taught about compass errors etc, the pitot error is never gone into in any depth. Consequently I for one sort of automatically assume that the ASI is always correct and fly by it, although if I stop to think about it that is obviously not the case. As Jellycopter said, it could lead to some interesting arrivals at the bottom of a crosswind descent.