In the eternal words of one of my uni mates at UQ: "Scramjets Suck"
In all seriousness, Scramjets are an incredibly difficult technology to make work across varying speeds as the entire engine needs to be designed around the bow shockwaves created by any leading edges. The problem is, these shockwaves change angle as you speed up and you lose efficiency and/or risk destroying your vehicle if the shocks don't contact the right points. Hence, you're entire vehicle (or at least the engines) need to morph as they speed up, and at hypersonic speeds, that's a tall order. At the University of Queensland, they were at one point investigating vehicles that would sweat COPPER in order to protect themselves form the hyper sonic heat. But, at a constant hypersonic speed for a short time, they are great (espeacially if they are...'disposable').
This has one very unfortunate implication for anyone working on scramjet research. It will really only have military applications, either as hyper sonic cruise missiles or hypersonic spy planes. As a space launch system where you have to constantly speed up and get out of the atmosphere ASAP, well as I said above, "Scramjets suck".