Some folks are just so wedded to those big, heavy bodies with the "pro" control layout and more AF sensors than anybody needs. AF is never more important than in sports, and the majority of the guys on the sports forum shoot with the center AF sensor in single sensor mode, regardless of camera.
The D600 obsoletes the D700, even more so than the D800 did, if for no other reason than it undercuts it in price. It surpasses it in resolution by a mile, and I am sure that as soon as we start seeing comparison tests, we'll see that high-ISO performance is superior as well.
As Stan alluded to: Unless you pound nails with your camera, or for some reason your ego or workflow has to have the "pro" control layout, the D600 is a far superior imaging tool to the D700, just as the D7000 is a far superior imaging tool to the D300 (the other "beloved" camera that people can't seem to get over).
That said, I also agree that Nikon intended the D800 to be the D700 replacement. The D600, like the D7000, is a new class of Nikon camera, designed to better define the differences in the product range, and avoid the canabalization that occured between the D700 and the D3.