From what I have read, biodiesel can mess with older (rubber) fuel lines and seals, and can clean sludge out of the fuel delivery system. It's generally recommended to change your fuel filter after using it for a couple tanks, and keep a spare with you in case of performance issues or a rough-running engine.
Unless the bio is poorly refined, I've not heard of it rusting anything out. It is however known to gel at up to 40F, so in colder climates it might be a good idea to either mix it with dino diesel or use an additive.