Reading my original post, I was skeptical about the new D300. Well, I'm eating crow now because it's much more than an "incremental" upgrade. No doubt some of you are considering the new camera, so here's what I've noticed so far:
Executive summary: It appears to be better than the D200 in every way.
I wasn't expecting to be impressed by the AF system, but it's in another league. My D200's focus was always off using the 85mm f/1.4 wide-open, but the D300 is dead-on, even without fine-tuning. 51 AF points ain't to shabby, either. (The D300 has an AF fine-tune function that remembers which lenses require how much tweaking, if any.)
3D tracking is pretty slick. The AF point actually moves across the frame to follow the subject. I have very little "action photography" experience but I got to try it at an RC airfield this weekend, and while the 80-200 f/2.8 I was using has the older and slower screw-drive AF, 3D tracking appears to be more than a gimmick. I hope it rocks with the 70-200 AF-S VR.
It uses something called "Active D-Lighting" which seems to be a dynamic range compressor that helps with high contrast scenes. Since digital doesn't have the same latitude as film, it's easy to underexpose when you're trying to keep the highlights from blowing-out. Active D-Lighting corrects that to some extent and helps to bring out the shadows.
It's faster. The first time you press the shutter you can hear and feel the difference. I have no need to shoot 8 fps, but I like knowing the camera can do it.
The new vertical grip is based on a flattened metal tube. Because of that, unlike the grip for the D200, it feels completely solid. It also has its own cursor button which is mandatory considering the 51 AF points. Some complain that it only holds one battery (the other stays in the camera), but I feel that it balances much better this way. It may even dampen vibration better since the camera body is effectively denser.
The information on the top LCD display can now be shown on the rear LCD screen. Excellent for tripod shooting. The 3" LCD also has room for 922,000 pixels so it's a lot sharper.
High ISO performance is a one-stop improvement over the D200, and it seems to preserve more detail. I haven't taken it to a concert yet, but it should be nicer. (Do yourself a favor and NEVER look at the high ISO images from the D3, they're too amazing.)
Auto white-balance actually works. I didn't notice if the D200 did this, but the D300 has sub-settings under "fluorescent" that include sodium vapor, metal halide, and different varieties of fluorescent (warm white, cool white, etc). I found these settings right away, so I don't THINK the D200 has them. It's not just about color temperature, these kinds of light sources have very irregular spectral distribution plots.
The remote shutter release connector has a captive cover instead of one of those tiny threaded caps that I eventually lose.
There's more, but these are the things that have jumped out at me so far. If anybody has specific questions, let me know and I'll try to answer them. Basically though... just get one, it's good
(And yeah, Dad got a hand-me-up D200.)