I thought it was important to share this with other D600 owners. For a few months I have been discussing sharpness issues with the folks in the Sports Forum, mostly because my basketball shots were not razor sharp.
One thing led to another, and my thought that my D600 was backfocusing resonated with some comments of another poster. So, I took the plunge and bought the Reikan Focal software and to date have measured the fine tune of 7 lenses on my D600 and a few of the same lenses on my D300s. Every lens required at least a -10 on the D600, (and some required -20) while the D300s was spot on or -1.
My early read is that sharpness has improved a lot. This I mention because I blew off fine tuning as "unnecessary."
of course, ymmv.
Visit my Nikonians gallery.