We have gotten used to cameras with amazing performance compared to the top of the line film bodies from a few decades ago. The Nikon F Series had a sync speed of 1/60th sec. The Nikon F2 Series and F3 Series had a sync speed of 1/80th sec. In the mid-1980's the F4 Series introduced a sync speed of 1/250th sec. and this remains to this day.
A 1/3 stop loss in sync speed is not the end of the world since the limitation will only be apparent in situations where fill flash is being used. Since the D600 supports FP High Speed Sync mode just like the other bodies the value of the extra 1/3 stop is minimal. Good Luck and Enjoy your Nikons!