1) I have a D300 & a D700 which I've been quite happy with, I like the compatibility of all the various battery systems, flashes, grips ect,,. I can see keeping the D300 for zoom work however would there be any point in keeping the D700 after purchasing the D800.
2) Is there any way of avoiding the often reported focus problem when purchasing a new D800 by picking & choosing,,searching for a later serial number, whatever,,. Have these problems been discovered on both CAN and USA sold models,,. Might it be better to buy from a dealer and test in the store,,.