Just think a somewhat more sterile ebony.
That's a good way to discribe it.
I've played quite a few fretless basses with ebonal boards, and have owned a couple ... IMO, they sound pretty good. Pretty close to ebony with more of a modern tone to it (a bit more hi-fi). The only thing I don't like about them is they always seem to feel cold, kinda like their tone.
Another thing I've found ... sometimes they can feel a bit cheap and uncomfortable if the edges aren't rounded off enough. I've had them on a MTD Kingston fretless 5, and a Cort Cubow fretless 5 ... out of the two, I prefered the feel of the Cort Curbow. To me ... the MTD sounded good, but felt cheap due to the ebonal.
When it comes to fretless ... I do believe ebonal to be a cheap substitute for ebony. However, I'd more than likely choose it over Maple, and prehaps Pau Ferro, if given a choice.
As far as fretted goes, I had a Cort Curbow 4 and didn't think twice about it. It's great for slap'n and tap'n! So I say, go for it! I'd be cheaper than ebony ... with more of a hi-fi tone. A perfect compromise to cost, with the same overall look.