I used to use ACARS software quite a lot, but although I have the AirNav software, I find that with so much information already available in the aircraft lists an on the map, I don't really have the time to look through the ACARS data. Very few aircraft seem to pass position on ACARS and even then it is so sporadic as to make tracking using ACARS a bit hit and miss (positions info is not used by the AirNav software anyway). If you are into collecting ACARS logs and going through these, then I can understand the need, but really ACARS has been left behind by new developments.