"Yet that's what has to work well to beat the competition, which is taxi dispatchers with paper maps, phones, and radios."

In some part (maybe even a large part) of the world, yes. But in markets where taxis are from different companies (or in other ways make ordering one in advance more common) already has fairly sophisticated technology. Let's not promote the myth of startup exceptionalism. Uber has modern (but not futuristic) technology, but the real difference is in the business model.