Wow, these are looking pretty incredible. Like many others here I did think that the Hi3 ISO setting was going to look pretty horrific and was a simple exercise in marketing. Whilst you (obviously) wouldn't wish to use this setting unless you really had too I'm still very impressed with what has been achieved.
The ISO 6400 shots look about as grainy as ISO 1000 on my D200!!!
The ISO 6400 shots look about as grainy as ISO 1000 on my D200!!!