Warp Drive is indeed viable - I've personally done the (some of, not all I don't have enough time) calculations and looked at the issues with it, and all of them are "solvable." (Although we have yet to test anything at all) First of all, the mass-energy requirement of the negative matter is only that of the mass of the voyager space probe, and even then you don't actually need negative matter. A scaled up version of the quantum casimir effect would generate the expansion of spacetime behind the ship needed, not to mention the (although highly remote) possibility of harnessing dark energy. The energy required to power the ship could be done with antimatter - we only need to find a more efficient process of creating and storing it. But you are right in that anti-matter wouldn't still be efficient enough to power a warp drive, as it would take an inpractical amount of it. We'd have to find something more advanced, dark energy has been suggested but is still only theorized. The build up of energy and heat inside the warp bubble can be counter-acted by metamaterials, which refelect all kinds of elctromagnetic radiation and are in development by the U.S. military. Stopping the ship is the only real problem, as you need to have the exotic matter projected in front of the warp bubble, which would require it to be tachyonic in nature. However, it might be possible to use quantum entanglement to make exotic matter stop the ship, although I'm not entirely sure if it would work. I will not dispute that Dr. White is indeed "selling" this idea as something practical, when it's nothing more than a viable possibility in the future. But I am excited by the fact that in a few centuries it could be possible, provided our civilization doesn't collapse by then.
