The sad thing is that the Arrow was ahead of its time; it was just designed for a role that turned out to be superfluous (intercepting Soviet manned bombers at Mach 2).
The engineers were even considering using it for a high altitude satalite launching plateform. It really is sad it was not developed. But we do know the same engineers took their idea's with them and went to work for NASA and such, so who knows just how much of their brainwork is in actual use today.