I have a D300 and I'm very impressed with good lighting - but the D3 has far better IQ, and a much faster AF. I've used both cameras quite extensively. I'll keep my D300 for backup, but the D700 with the new chip and it's AF system really is, for me, a pretty significant improvement in my pictures. I'm first on my pro dealer's list, which gives me a couple of weeks to make up my mind. I was'nt swayed until I covered boxing last week - and used both D300 and D3. No comparison when it comes to getting THE picture.