I bought a bamboo shirt from a fitness store several months ago and I've been pretty happy with it.
I was looking for something that was anti microbial. Most of the poly/wicking workout shirts start to hold on to gym odors after a while no matter what you wash them in. The clerk at the store said that bamboo and stuff treated with silver were both supposed to keep odors under control.
So far the bamboo shirt does not smell and wicks as well as any of my other work out shirts.