I did not think the DK-17M did much when I first tried it.
I then took 500 pictures in the field with Zeiss MF lenses, mainly the 21 mm f2.8. The pictures were close-ups of ground orchids and their surroundings. Most close-up subjects were nailed by the third exposure. Environment shots were spot on first go. My partner in this rapid survey of marsh orchids and their hybrids, used another 800E with a Nikkor 35mm f1.4 AF-S. I had done an AF Fine Tune on this lens and almost all her photographs were in focus at the point intended. So AF is better than MF, but I still like the MF lenses and I like to choose the focus point anywhere in the field without focus and compose. With hand held close-ups I find it is enough to compose and focus and hold simultaneously. We had to work fast to get the number of pictures and to cover the ground - and it rained most of the time.
When we finally found a very rare plant after six hours searching just for it, the tripod came out. Then the umbrella to protect the camera, and a Hoodman loup to focus LV. Then to wait while an ant walked in and out of the flowers. A good half hour to photograph one small pale green flower! Then to retreat carefully covering our tracks to protect the location from less respectful hunters.
Now to the point of my reply. In analysing our haul I found the above results and so experimented with my focussing. Including taking off the DK-17M at one point, but my success on the test targets was much less with the standard eye-piece, so it went back on. It is the best help I can get without going to LV.