From what I've seen, the Civ IV community is a little bipolar about Beyond the Sword. Some people view the expansion as adding a wide selection of previously overlooked features (espionage, corporations, and such), but others see the additions as little more than mandatory tedium. My opinion, for what it's worth, is that the expansion pack adds some great depth to the game, but needs some fine-tuning in the realm of maintanence and AI. The latest patch promises to resolve my quibbles about corporate maintanence and is supposed to enhance the AI's ability to utilize new features of the game, but I've not put much time in under the latest patch, as I've had other endeavors distracting me.