clicker, I have used the ZM 18, 25, 2/35, and 2/50 uncoded on my M8; these lenses are excellent and the results were impressive... optically at least, no so sure about the artistic merits! The widest three are off at DAG Camera Repair being coded and focus-checked. I also have the 4.5/21mm, which upon ordering it I had the store ship directly to John Milich for coding. Great lens; small, sharp with character, but on the slow side.
The coding is useful in adding focal length info to the EXIF data in the photo, plus of course in assisting the camera computer in making corrections to corner light fall-off, and to the cyan corner fringing caused by use of the IR cut filter. These issues can alternatively be taken care of in post processing using CornerFix software.
You can also use the lenses without the coding or cut filter. This is what I did at first. But there were too many instances where the IR sensitivity was a problem for color results. Some are of the opinion the IR content actually improves the look of B&W conversions. But information suggests that sharpness suffers without the IR cut filter because with non-apochromatic lenses the infrared is focused at a different plane than visible light, slightly fuzzing the image. Worth trying, though, both color and B&W, to see for yourself. 🙂
I have tried the hand-coding too, and this is a fine temporary way to see what coding does, even trying different codes, but with lens-changing the marker ink rubs off.