Summary: -but very useful if you find yourself in tight corners. Sometimes the old DSLR, versatile as it is, needs a useful addition such as this. Allows full 360 degree rotation of the eyepiece, instead of having to crouch or bend to use the viewfinder. Has a zoom capability too. My only quibble is that you are still viewing at 90 degrees to your camera, so that in itself is a minor limitation. If you can see the stock image beside this review, you may understand that point.
Summary: For me yes. The only time it's not attached to the viewfinder is when I've a Speedlight attached, otherwise this DR-5 stays attached. I can bend my legs/ squat so that my D800 is a few centimetres above the ground, or I can set my tripod to hold the camera just above the ground. Thus, I'm able to get almost impossible to get dramatic shots. With my Nikkor 14-24mm f2.8 the results are spectacular. Works flawlessly for portraiture as well.
Summary: As expected, this item is up to Nikon's usual high standards, both optically and in its build quality. However, it rates only four stars because of my only gripe; it's such a fiddle to fit and remove. I already own the DR-6 which fits my Nikon D80, and this simply slips over the viewfinder via groves on either side, but the process is much more involved with the DR-5. First you have to close the viewfinder shutter, then remove the collar from the viewfinder.
Summary: Excellent piece of kit for the copy stand and odd angles on the tripod. Build quality doen't feel quite up to Nikon's usual standard, though the optics are fine. Diopter ring is far too easy to tweak during use, mucking up the focus.
Summary: Bought this to use with my Nikon D700 when wanting to work with the camera set really low on the tripod or even on the ground. The optics are outstanding and the quality of construction is what one would expect from Nikon. Not a cheap item, but value for money in terms of results and the fact that it will last a lifetime if looked after.