ross b , Jul 01, 2012; 01:28 a.m.
Nikon claims these improvements on the D3s from the D3 per wikipedia:
Nikon claims improved ultra-high image sensor sensitivity with up to ISO 102400, HD movie capability for extremely low-lit situations, image sensor cleaning, optimized workflow speed, improved autofocus and metering, enhanced built-in RAW processor, quiet shutter-release mode, up to 4,200 frames per battery charge and other changes compared with the D3. It was replaced by the D4 as Nikon's high speed flagship DSLR.
I looked up the D3 at KEH.com and they want $2444.00 for one in EX+ condition. Also KEH offers a 6 month warranty with their used camera's. KEH does have a D3s for sale also and It is $4400.00 for an EX+ model. I do not know if you live in an area that allows shopping at KEH but it does give an idea of the used retail value of the camera's in US dollars.
The last point is that I have never owned, used or even held these camera's. Just info from the net is all that I have to offer.