I don't have personal experience with bamboo mattresses but here are some pointers given to us by the owner of an independent mattress store when we replaced our mattress.
Country of origin, you don't want to sleep on a mattress off-gasing toxic chemicals.
Longevity, especially the cheaper brands/models start to loose their elasticity after only a few months.
However, bamboo fibers supposedly wick moisture and body heat more efficiently away from the sleeping person compared to memory foam.
https://www.slumbersearch.com/bamboo-mattress-reviews