To add to what Gary & Brian have said, the cameras that do 1/500 sync are CCD devices which have a mechanical shutter capable of something like 1/200 fastest and use electronic means to "simulate" faster shutters. As such, they really have no limit to flash sync since the entire CCD is exposed at one instant regardless of shutter speed.
Today's sensors are CMOS-based and along with the great high-ISO performance, this tech allows things like LiveView (and by extension, movies) which CCD wasn't capable of. Also, this allows faster frame rates, but they're more difficult to electronically shutter.
As to the 1/200 sync speed, it means nothing to me (not a big flash user) but in considering D600, despite being the cheapest full-frame DSLR on the market, the gap is just close enough to D800 that at some point any potential buyer has to ask, why not just spend the extra $900? I'd only consider D600 as a backup to my D800. I'm leaning more towards the idea that this is not a smart buy for me.