This Stratolaunch concept does provide some advantages vs conventional launchers. It is less sensitive to local weather conditions. The rocket can be returned if the launch gets scrubbed. The launch can be performed at any location/direction the aircraft is able to fly at. And the aircraft can be re-used for dozens of flights.
SpaceX was originally the company that was to supply the launcher. But they backed out. Then there were issues with their replacement launcher from Orbital. They still have lots of issues to resolve, but I think they have the resources to see the program through. Ultimately, this will be a better approach than that of SpaceX.