>Do you really think the D7000 will out-focus your D3s?
No, but it offers me other advantages. Like 3D tracking and auto-area focus.
>Or better it above ISO 800?
Above 800, no. But at base ISO, which is where I tend to shoot most, it offers more MP, and more dynamic range. And if I don't have a need for the high FPS or high ISO, the D7000 gets the call before my D3s does.