You can expect it to feel very smooth to the touch. Sound-wise, expect nothing IMO.
It seems that folks who dislike pau mostly complain that it doesn't "look" like dark rosewood. Personally I like pau more than the typical rosewoods that are available nowadays. It's not like Brazilian rosewood is an option anymore, so....
The most beautiful fretboard I have is the Brazilian RW slab on my Telecaster. It was made for me in 2000ish when there was less issue with rosewood in terms of customs though still 'banned'. It was recycled from old furniture use, and thus sustainable. When oiled and not neglected it's really stunning. I don't have any issues with the Pau Ferro on my Dingwall Voodoo Prima, it's fine...medium color tone, medium grain, etc. Nothing bad, but definitely not a 'stunner'.
I also have a bunch of other Rosewood boarded stuff, some Indian, some farmed (maybe Indonesian? I'm not sure), that all looks the part of dark brown with darker grain throughout. It's all fine. My maple boarded instruments are also great. I've had a lovely bass with a wenge board and would totally do that again too.
For fretted bass these days I'm favoring my newest, a Dingwall Super P that has a really thick Macassar ebony slab that is dark and even looking.
In my playing experience the 'system' of your bass as a unit is much too complex to point to any one piece of wood as an explainer of much. You've got numerous pieces of wood put together in different ways, with different densities (no matter the type of wood), different consistencies, different geometries and levels of fitment. You've got variables in hardware (everything from the nut, to bridge to neckbolts, different electronics with levels of component precision. Does any one piece count? Sure. But they all count in different amounts and different ways based upon the actual instrument.
That said, as I mentioned before, when dealing with fretless where the wood IS your witness point rather than a fret, I'd consider it more of a contributor than otherwise when you've got a piece of metal for contact. There's also considerations in the surface, how hard it is, how well it will stand up to continuous wear, etc.
...So I generally think of the fretboard in terms of instrument aesthetics. I'd kind of like to do one with a super-figured piece of Ziricote if that's feasible for stability reasons.

We haven't even mentioned that one yet.