I hope to have a Nikon D3 in hand by the end of November (see my August 23 comments). The one thing that surprised me in re-reading the specifications is that it has no anti-dust capability, unlike the D300 and the Canon EOS 1D[s] Mark III cameras. That’s a pity, as I’ve grown accustomed to the hassle-free cleanliness of the Canon EOS 1D Mark III.
The D3 apparently offers the choice of either 12-bit or 14-bit color, making for an interesting possibility for comparison: do the extra 2 bits actually make a difference?
The dual Compact Flash slots are a refreshing improvement over the bifurcated Compact Flash/Secure Digital approach used in the Canon EOS models—buying two types of cards (mismatched in size), card readers, etc never appealed to me. The D3’s dual slots can swallow cards of matched size and speed, excellent for live mirrored backup, or offer the astonishing prospect of 32GB of internal storage.
Also unclear is whether the infrared-blocking glass will be removable eg whether the D3 can be turned into an infrared camera. While I’m pleased with my Canon EOS 5D-IR (see diglloyd Guide to Digital Infrared), the lack of Live View on the 5D makes obtaining precise focus in infrared more of an effort and more prone to error. So a Live View infrared camera is high on my list of priorities. My workhorse EOS 5D-IR will be for sale should I convert a Nikon D3 for infrared use.