I have purpleheart on my fretless. My fretless is a neck-thru and there are two purpleheart stringers between three pieces of maple. Purpleheart, as I understand it, is a very hard and strong wood. On my bass it really adds to the look of the bass as it is sandwiched between the lighter colored maple.
Here's a pic of my Wishbass from the rear where you can see the purpleheart.
These pics are before and after I waxed the bass.
Pete