Intro: I bought the D200 as an upgrade to my aging D70. The difference between the two cameras is noticeable, mostly in the feel, build quality, performance and image quality. The D70 (now replaced by the D80) was a high end consumer level body, while the D200 is a professional level camera. It makes an excellent backup to the D2Xs and is well suited to travel photography where weight is a limiting factor. Feel: The camera feels great in-hand as I have come to expect from Nikon. The viewfinder is greatly improved over the D70, brighter and clearer, while showing you everything you need including ISO, focus, exposure, aperture, shutter speed, metering mode, images remaining on the flash card, and when the shutter button is pressed halfway, the number of images for which there is room in the buffer. The flash is well positioned on the body to prevent lens shadow on most lenses, however shadows will tend to occur on some of the larger wide angle lenses such as the Nikon 12-24 DX, but not at all focal lengths. At about 16mm the shadow is no longer visible, and only at 12mm is it very apparent.

The body is composed of a magnesium alloy core for strength and rigidity and a black plastic outer casing. The core gives the body a very good feel in the hand and it does inspire confidence in the camera. I have dropped mine (not intentionally) and other than a couple small scrapes on the black plastic casing, there is no damage. The grip is rubberized in the typical Nikon fashion and is quite comfortable, even for long periods of time. The body has weather seals that resist the elements quite well. I've used the camera in rainy conditions and have had no problems. Be aware however, that the lens mount  has no such seal. The only lens so far that I have seen that has a sealing ring is the Nikon 18-200VR. If you have to  use the camera in heavy rain, then I suggest either a rain cover, or using a plastic bag. I have not used the camera in such conditions yet, so be warned.

The D200 is a fair bit heavier than the D70 and it is bigger. Adding the MB-D200 battery grip makes it just slightly bigger than the D2X but the added convenience of the grip is amazing. Definitely one of the better accessories for the camera. You don't realize how much more comfortable the camera is in your hands with the grip attached. It's easier to hold and manage. If you have small hands however, adding the grip might make the camera a bit too large to handle. The grip allows you show portrait shots while keeping your hands in the landscape orientations. Both front and real command dials, shutter release, Af-On button, and release lock are available on the grip, plus the ability to use AA batteries in case you run out of battery packs

Images: The camera produces decent jpegs straight out of the box, but it does need some fine-tuning to produce stunning results. This is by no means a fault of the camera itself, but has more to do with all the possible combinations of options in the custom menus. If you are after a DSLR that shoots awesome jpegs right out of the box without all the options and the need for specific setups, then I would suggest a D80. RAW images with the D200 retain a noticeable amount of highlight detail, especially in areas like clouds. I was not able to tell the difference between using compressed NEF (approx 10mb) vs. uncompressed NEF (approx 16mb). From other reviews and forums I have learned that apparently there is even more highlight detail saved in the uncompressed version, however I have yet to see a difference visually when comparing identical images. If storage space is not a concern then uncompressed NEF is obviously the way to go, provided you have a powerful enough computer to handle 16mb files and well as batching and group processing. Travelling I usually have 3 or 4 4GB flash cards and a Hyperdrive Space storage unit to back up in the field. It is the quickest way to backup photos on the fly and the units are quite small.

Resolution: The resolution improvement, 10mp D200 vs. 6mp D70 is significant enough to sway buyers to the higher resolution cameras. While cameras should not be bought based on MP size only, it will make a difference in post processing when you try to crop and zoom in on parts of the image. The higher resolution also allows to make larger prints. The CCD is positioned deep inside the body, making it a little difficult to get at for cleaning, but not impossible. Just takes some nimble fingers, steady hand and practice.
Just keep in mind that the higher the resolution of a camera, the better quality glass you will need to be using. It is common for high resolution camera sensors to outperform some of the lower quality glass that is out there. The sensor in fact is able to capture more detail than the lens is able to deliver/resolve and your image quality will suffer. Handholding technique also becomes very important, since incorrect technique will result in poor image quality and very few keepers. This became obvious to me the moment I started using the D200. Most of my shots were blurry shooting handheld, but even when mounted on a tripod they were not what I was hoping for. The couple of lenses that I used with the D70 were no longer useable on the D200 and their faults became obvious. Upgrading to high quality glass makes a huge difference, as well as learning to hold the camera better.

LCD: Large LCD. Very useful for reviewing those wonderful RGB histograms and checking for image sharpness. One handy feature is to set the multi-selector button function to zoom in to high magnification while in playback mode. This lets you check for image sharpness. The LCD is easily viewable even with the brightness set to minimum, and in sunlight. The screen protector sometimes causes reflections making it hard to see the image in bright sunlight. Good protection for the screen though especially in rough conditions. Replacement screens are available from almost any camera store as well as online and are only a couple of dollars.

Buttons and Settings: Gone are the specific scene settings such as macro, night etc. I found them useless since you can make those changes yourself with more control than letting the camera override certain aspects. Instead you have three buttons, Quality, WB, and ISO. Below them is a rotating wheel that adjusts image rate of fire, Single Shot, Continuous Low, Continuous High, Timer, and Mirror Lock-Up. Metering modes and focus modes now have their own dedicated body controls, and save you from scrolling through the menu. A programmable Function button above the aperture preview button is very useful. The camera has a "lot" of custom settings and the ability to preset 4 custom shooting menus for specific occasions so you don't have to adjust them each time. The ability to switch between focusing modes and focus areas using external buttons is just priceless. Metering can also be changed instantly with just a small rotation of a knob. Very handy to be able to do this on the fly without entering the menu system and wasting time (and battery life).

Performance: Focusing is accurate and speedy with the 18-200 VR and the 12-24 using the new 11 point auto-focusing system.  It is better than the D70 but not as good as the D2X which uses more cross type sensors and hence part of the reason for its much higher cost. The 5fps continuous shooting rate is very useful for fast action photography. The rate is adjustable for low and high fps and whether release priority is set to focus or rate. Setting it to focus will make the camera give more consideration to making sure the subject is in focus, while rate release priority ensures that you are getting the maximum fps out of the camera regardless of focus. The flash is accurate and produces properly exposed images even in difficult lighting conditions. The camera handles complex lighting and colors really well, preventing overexposure of bright areas quite well. It still does happen once in a while but I find that it is usually my fault rather than the cameras. The camera buffer size is huge. It will hold 21 NEF files and write to the card as fast as the card can handle it. This is an awesome improvement over the D70, giving fast action photographers plenty of room to use. In over 8 months of shooting I have yet to fill the buffer and run out of space. Memory cards with fast write speeds are very important if you shoot sports or action sequences regularly. 

Battery Life: This is the one area where I would like to see some improvement. Nikon advertises 1800 images on one charge. I have never been able to come even close to this number; instead I average about 450 to 700 shots on one charge depending on  how much I use the LCD. Now this is with 16mb NEF files so you might expect about 20% more using compressed NEF and around 1200 jpegs or so if you don't use the LCD too much. That wonderful screen has a fairly high power consumption. I usually use the screen once in a while to check for image sharpness and histograms and not much menu browsing as everything is preset in the separate menu banks. The longer you play with the menu the faster the battery will die. My D70 never ran out of power. Even after a week of shooting, and over 2000 images, quite a few of them with flash I was not able to run it down. Long exposures on the D200 will also deplete your battery very quickly. Buy at least 2 or 3 spares if you plan on longer trips and bring a adapter so you can charge it in your car. Three batteries are usually enough for shooting NEF, 2 will do for jpegs. As mentioned before, the battery grip is very useful not only for portrait shots, but also for long shooting sessions. It can also take AA batteries in case you run out of charged battery packs, or are in a location where charging them is not possible.

Trap Focusing: This is a very cool feature that lets you prefocus on a specific location, and once something comes into that specific focus distance the camera will take the image. To do this automatically you will need a remote release, preferably one on which you can keep the shutter button depressed. Set the release priority on the D200 for focus.

Set the auto-focus switch to C or S.

Set the custom menu setting A6 to AF-On only.

Set the release priority for focus for either S or C. This is very important as it will prevent the camera from taking a picture without there being an object in focus.

Prefocus on the determined distance where you expect your subject to be, using the AF-ON button. You do not want the shutter button controlling focus as you are pre-focusing. You only want the shutter button to fire the shutter. Once you are focused, release the AF-ON button.

Now back away from the object. Fully depress the shutter button and the camera will not fire. However when something comes into focus, the camera will start taking pictures.

This is very useful for unattended photography for nocturnal animals, birds at feeders etc. Also quite useful for motor sports as you can prefocus on a spot where say a race car will be and then the moment is arrives the camera starts taking pictures. It is much quicker this way than tracking the object and focusing at the same time, the camera reacts much quicker than the human finger. 

Cheers