If your thumb is feeling the fingerboard, you're doing something wrong. But, I will say that by the time Warmoth gets done surfacing the thing, a Wenge fingerboard is a fine thing. I've only played one, and was surprised at how comfortable it is. It's a very hard wood so it works well there, given some substantial frets that keep the strings off it. Its hardness is almost like a machined surface, so it doesn't get in your way at all.
That said, I don't think I'd use one for a fretless anything because it does have some seriously coarse grain to it. That's liable to make it somewhat noisy and/or inconsistent in intonation. Also, that grain is a grunge trap that's nearly impossible to clean, if that matters to you.