It forms the basis for determining ALL characteristic speeds displayed on the PFD.
On the two brand new A319s we have just had delivered all the PFD displayed speeds (green dot, vls etc etc.) are now generated by the FMGS rather than the FACs as before. Not quite sure why they are now doing it this way but it does away with the differences that you notice in the speeds on the the other aircraft. I have to say that in 7-8 years of flying the thing I have never once felt the need to dive into AIDS to find the "true" weight. I have long suspected that the information derived from the angle of attack vanes is just as prone to error as those derived from loadsheet weights, a tiny error in the measured AOA has the potential to generate quite a large discrepancy in sensed weight I would have thought.