I have pau ferro on a fretted Warwick Streamer and on the Fender Jaco fretless jazz and I like it a lot on both. In fact, I liked it so much on the Warwick that I was giving serious consideration to using it on a custom bass. I loved how warm the tone was, albeit it’s difficult to discern how much of that is down to the fretboard wood and how much is down to other factors.