I am a D300 owner and have been happy with the build quality. But, at the same time, I admit to being biased towards gear "Made In Japan". Given the choice I would buy the item made in Japan. Even if Nikon has supposedly implemented good QA practices in Thailand.
Regarding the D700 I would assume they would keep manufacturing the camera in their Sendai plant along side the D3. I mean they are sharing the same processor. Why would they not keep manufacturing it in the Sendai plant. That and one of the posters said they just expanded the plant.
So tempted to pick-up a D700.
On a side note (for the moderator). As I was typing out my reply suddenly the cursor would end up on the subject line. Odd.