I received my Katz Eye Focusing screen with optibrite treatment installed on my Nikon D200 last week. My results are mixed.
I elected to have the screen installed by Katz Eye Optics. I did that because they stated that they will confirm that the focusing screen in properly adjusted for manual focus (my D200 native screen was a little off). The communication with them was excellent. They had a screen available to install in my camera three days after I placed my order. I sent my camera in and received it back promptly. The packaging was fine and I received an email telling me when my screen was ready, an email when they received my camera, and another email with a tracking number when the camera was shipped. I asked several questions via email and always received a prompt and courteous response. So far as I can tell (I'm going to do more testing) the focus calibration is right on for manual focus (auto focus is supposed to be unaffected by the focusing screen change).
Now, the not so good news. The screen works great for fast lenses. The split screen prism works well down to at least f11. However, the microprism surround (which I want to use to focus on fast moving people and animals) works well only to about f 3.2. My 500mm lens is f4 and with a moderate amount of effort it works a little better than OK but certainly not great. With a 1.4x teleconverter on the 500mm lens I can get the microprism to work with great difficulty. I can't get the microprism to work with a 2x teleconverter and the 500mm lens. When the microprism doesn't work, it appears as black area around the central spit screen finder right in the middle of the view finder.
I have a 70-300mm AFS f4.5-f5.6 VR zoom that I used to photograph my kids sports. The Katz Eye focusing screen is a pain with this lens. The microprisms only works at short focal lengths and then with difficulty. At longer focal lengths, the microprism is a simply a black area in the center of the view-finder.
I'm going to work with the new focusing screen for a while to see if I can get used to the microprism. I'm so disappointed, though, that I will probably switch back to the old focusing screen.