The bamboo diapers are softer than cotton, they are as absorbent (but thinner, since bamboo is more absorbent than cotton), but they take more time to dry than cotton.
As for durability, it's too early to know. They have been out for 2 years and a bit (out in June 2007 I believe), but most (or all?) of the first batch was replaced by ME (at no cost to customers) as there was an issue with the binding. A few people have had durability issues with the new ones (bald patches), but they are rare and I believe ME has replaced their diapers when justified. My diapers are about 15 months old and still going strong, but I doubt anyone has been through more than one child yet... It's still a bit of a gamble, unfortunately.