While I would like to see a Mustang with a good IRS setup, I don't mind the live axle, and there definitely is a need for one since so much of the Mustang is based on drag racing. The S197 is a nice handling platform I think, I went in a little gun shy about the handling after owning some nice handling IRS vehicles before this, but I was impressed with my 06. I think too many critics made up their mind about its capabilities without really wanting to give it a shot. Pre-05s definitely felt sloppy to me in comparison, so I can see where some prejudice might come from.
Regardless, if it ain't broke, don't fix it.