I got some polyester underwear... they are the bomb. Beats cotton as far as nastiness goes any day. If you ever go camping polyester underwear are a god send because you can just jump in the water with shorts and undies whenever you like and you dry off in minutes.

but yes, all synthetic sports gear (and non-synthetic as well) has a tendency to stink. The more breathable and wicking it is the more the stink particles have a chance to be stored and emitted into the atmosphere. And Rob, I'm willing to get your bike shirts smell bad, but I'm not willing to prove it.