Too many players associate the fretless sound with just slides, mwah, lyricism etc, and there is so much more to it than that. Because your fingers are stopping the note you have no much more control of the note's envelope, both in terms of the overall envelope and the envelopes of the individual harmonics. If you have a soft board, then you can only do so much to get more sustain, particularly of the higher overtones. If you have a hard board then you can let your left (and right) hand(s) control the damping you require.
My fretless has a polyurethane coating on the rosewood board. Not as hard as epoxy - probably not as hard as ebony - but it's holding up really well, especially considering the amateur job I did on defretting, filling, sanding and coating!
Alex