IMHO, the classic test equipment products had it right. Look at the big boat anchor Tektronix scopes like the 545B and such. They had etched/engraved panels with colored fill. The labels couldn't come off and the controls were grouped together with a colored box around each channel. Lines would lead you to certain related functions. It's subtle, but a lot of thought went into those panels. Hewlett-Packard got it right most of the time too. Even if the layout was cluttered, it made some kind of electronic sense, and your fingers tended to go to the right knobs automatically. Ditto General Radio Corp. All those companies had exquisitely detailed manuals that explained not only how to use the instrument, the relevant equations for the type of work, the internal circuit overview and theory, the actual circuit operation and complete schematics that were large enough to fold out and read. Man, I sound like some old fart lamenting the loss of the past and claiming to have walked 5 miles uphill to school- both ways.