I've had bamboo boards in stock for almost two years and I've never seen any cracks, in my experience the surface gets scrached as easilly as any other board though.
I don't have any special storage with regards to humidity/temperature but store some in my house and some in the garage where temperature varies between 30c and 10c so I'd say that they are pretty resistant from cracking, but it may of course be a problem in more extreme situations (e.g. in a desert or leaving the board in the car).
And I only have experience of solid boards, and I suspect that those could be of various quality too depending on where and by whom they are fabricated.
I have written earlier on this topic that there
may be a higher risk with boards that have etched lines, as opposed to painted, but I haven't heard from any customers that this is a problem either.
As for the sound, I'd say that it is much more crisp than with a softer board, but again this is for the solid boards.
This, and also the Chinese vs Japanese size is much according to taste; some like the crisper sound and some don't mind the gap with Japanese stones on a Chinese board.
For reference, this is a bamboo board with 22-22.5 mm jade stones (Slate/Shell are 21.5-22 mm as are most glass stones I carry)

/Mats