It is used because it is considered a Greener material. Salk I believe charges about 700.00 extra for Bamboo
I wonder if it also may have different resonant characteristics than traditional cabinet materials (MDF) making it better, or worse, than those(?)
Laminated toilet paper is better than MDF, or at least equal. Seriously, I hate MDF ... and if you knew how easily air passes right through a 3/4" sheet of MDF when laid on a vacuum clamp CNC table, you'd NEVER use it for a speaker cabinet.
I've played with bamboo ply's before, and don't think they offer anything over true Baltic Birch ply. Either is a huge step up from MDF. Another product you should be able to get easily from local hardwood stores is MDO, Medium Density Overlay. It's a nice quality ply with each face covered in a resin (epoxy) soaked paper veneer. The paper is then applied to the ply under heat and pressure, and is very hard ... completely moisure resistant. In fact most road signs are now made from MDO. It's an excellent surface for painting, or for applying veneer, and it's relatively inexpensive ... and very strong.