If I about to choose to system, I'd be stuck between the D200 and the D40 as well.
Apart from all the technical aspects, I just find the Sony A700 to be very..um..ugly. It somehow looks like an unfinished prototype, like those flash cars you see on autoshows. Bu I'm sure it's a great camera.
That D300 though, that is going to be a serious piece of kit.
This probably belongs to the Nikon forum but just for asking,
Will it (D300) have the full remote shooting (from a PC) mode like the 40D? For me, that is much more important than something like an HDMI output.
Regarding the D300...yes it does support WiFi wireless file transfer. Networked even.
And I too find the A700 very ugly. Looks like a child's toy. And if you view the video clip here at Cameralbs for the Sony DT lens you'll hear how LOUD and chep sounding the AF in-camera motor sounds. And the cheap sounding shutter release sound. Matters to me. One among many reasons why I prefer getting either the D300 or 40D. They are built much better inside and out.
Just waiting for the test reports for the D300. Which will include comparisons to the 40D and A700.