I find a unitary system that clearly devolves (thus being granted by the central authority) certain powers to the subdivisions to be ideal. Federalism in the United States is excessive. Many other federations are merely in name.
The main fault with the current Federal system in the U.S. is that the lines between the Federal and State governments are too often blurred. Take for example, Medicaid. Ideally it should be either a pure Federal program like Medicare is or a set of pure State programs with no Federal input.