Thank you everyone . . . you all sound pretty persuasive and reassuring - lots of tangible benefits to an ebony fretboard overlay, with no negative effect on sound quality. Guess that's the way I will go on my next dulcimer! 
Larry
Appearance preferences aside, I am curious how an ebony fretboard overlay affects the playing ease and/or acoustical qualities of a dulcimer compared with having a walnut (or other typical hardwood) fretboard with a lacquered finish, or a walnut fretboard with an oiled finish (currently I only have experience playing the latter two types).
Assuming the surface is kept clean and the strings periodically slicked up with Fast Fret (etc.), does ebony add any speed or ease of moving between frets? Does having that second, thin layer of wood glued atop the fretboard have any effect on sound quality or volume, compared with a fretboard that is one single piece of wood?
I'm hoping someone with experience playing all three (ebony, vs. lacquered, vs. oiled) might have some thoughts to share. Many thanks!
Larry
