If you are reading this, then you're tempted by a Full Frame DSLR. I owned a Canon 40D - a camera I loved but crucially it lacked the true wide angle capacity of film cameras and I have always disliked the cropped images produced by most DSLR's.
The D700 or any FF is worth it on that count alone.
Choices for the non-millionaires are therefore the Sony A900, the Canon 5D Mk II or the Nikon D700 (although they are all still too expensive).
The good news is that there is not a turkey among them; the image quality is fantastic with all three (I only quote from the ludicrous number of reviews I have sadly read).
My choice was ultimately driven by the way in which I use my camera rather than the spec sheets, as the three cameras all point at a different type of photographer. This camera would better suit the intermediate or advanced photographer, as there are lot of menus to learn and much room to configure or hang yourself. On the other hand, the progamme mode does make the decisions for you, although even then you can change the settings.
I mainly use the camera for shooting (in order of importance for me): my kids running around (speed), portraits (IQ), plays (low light) (speed), rugby, football matches (speed) and lastly landscapes (detail).
I wanted a camera that was fast, had great image quality, worked really well in low light and was FF. On all those counts the Nikon is probably the best package. The Sony and Canon can resolve more detail for landscapes or architecture and can be blown up larger, they probably have the edge in studio / stock photography work.
The Nikon produces skin tones beautifully and is the best performer in low light, although the Canon comes very close (again from my reading, I don't own one).
It is worth mentioning the low light ability of this camera and by that, I mean the ability to shoot at higher ISO than anything else around, yet produce excellent images. You can be shooting handheld, in virtual darkness and produce quality images. Living in the UK, this was really important to me (we specialise in cloud) and the camera is truly outstanding in this respect. Even when there is noise, it is grainy and film like; ultimately it is usable rather than unusable. Less pixels than the competition = larger pixels; this translates into an ability to pick up more light.
The Nikon is much better thought out than my 40D - it is more comfortable to hold, it is easier to change the settings on the fly (you tend to spin dials on the camera rather than having to delve into sub-sub menus), it is more ruggedly constructed and more configurable but on the other hand only has half the resolution of the Sony or 5D MkII. However, it blows up to 50cm by 70cm without pixelation (that's as far as I have got) and beyond that it's academic for me, as I don't have a house big enough to cope with larger prints. For some the ability to resolve the finest detail in landscapes may be more pertinent.
You do need to fiddle a little more with the in camera settings to get the sharpness, contrast etc that you want for your shot but the camera is so configurable that you can really control your output.
The autofocus is excellent on the Nikon (superior to the competition) and I have the grip which gives me 8fps when needed (it did mean buying another memory card as they don't last long on machine gun mode).
The quality of the images I have produced from plays, landscapes and action is really high - note the quality of the images is high, not necessarily the photographer (some of my landscapes in low light are on Flickr, type - Sun Setting Over Woodingdean into Google).
I am really happy with the D700, mainly because it suits the type of shooting that I generally do and is a great all-rounder.
How helpful would this review be to a person making a buying decision? Rating guidelines