The only significant difference is that Nikon will not service the import (Gray Market) units.
That means that you will need to go to the retailer for any warranty work (the good retailers like B&H provide 1 year warranty on imports) and even after the warranty period you would need to send the camera to an independent repair facility if you had any issues.
If you go with an import just be sure that you get it from a a well-known retailer with a reputation for good service.
Many online vendors selling Nikon cameras at rock bottom prices DO NOT include all the items you would get "in the box" if you purchased a Nikon USA body. Imagine paying extra for a battery and charger. Don't laugh, it happens.
________________________________________ 45+ years of Nikon ownership and counting Visit my SmugMug gallery
I wouldn't buy it because of the known D600 issues with dust and oil getting onto the sensor. If it ever needed service you'd have to find someone other than Nikon Repair. Nikon no longer provides parts to camera repair facilities making it even more difficult to get repaired.
If the price is significantly lower than other outlets, check the dealer rating at http://www.resellerratings.com/ If they are one of many on-line crooks promoting cameras on their web sites, the web site above probably has a record of them. If they do not have a record of them, it means they are new and probably just changed their name to avoid prosecution. Deep discounts are the stock in trade of hundreds of rip off on-line sellers located in New York and New Jersey, that specialize in rip offs. With the thousands of complaints filed it is amazing that those two states have done nothing to close down these outfits. The typical deal is for a import or even a new stock camera but when they call to get your credit card info, they ask if you want the needed accessories like $150 battery, $250 charger, $80 strap, $100 SD card. If you refuse pay extra for items normally included, they cancel the order. Stan St Petersburg Russia
As Stan points out above: Be very careful who you buy from. If the price looks too good to be true, they are more than likely scammers.
If you check the Nikon USA website, Only Nikon Service is authorized to service the D600. If that is the case, getting service for a gray market D600 will be very difficult via any other source than the Dealer you purchased the camera from.
If you want to save money, I recommend the refurbished D600s sold by reputable dealers such as Adorama, B&H and Cameta. They are USA cameras and include a 90 day Nikon warranty. They include all of the accessories sold with a new camera.
I purchased my refurbished D600 from Adorama for $1599. I joined their VIP club for $7.95 which adds an additional 1 year warranty from Adorama for all purchases. The refurbished camera had only 15 shutter clicks and looked completely unused.
I agree a refurbished one is the way to go if you want to save money. I to bought a refurbished D600 from Adorama and with the Vip warranty you get 15 months of protection and my refurbed D600 looked and felt new the only difference is the box instead of a shiny gold box you get a silver box that says refurbished product.