The MongoDB Java Driver 3.0 is designed with several key goals in mind, including consistency, cleaner design, an intuitive API, understandable exceptions, test friendliness, and backwards compatibility. The driver aims to address inconsistencies in the existing codebase, improve maintainability and extensibility, and provide a more idiomatic experience for Java developers. The new design features a Core layer that provides a backward-compatible API, which can be wrapped with an additional API for other libraries to reuse common functionality while providing their own API. The driver also introduces specific exceptions for exceptional cases, makes use of interfaces at the API level for testing, and prioritizes backwards compatibility.