The ABL has yielded many many benefits: modeling, control systems, adaptive optics, laser chemistry, CFD analysis. Yes, in the end it has to actually be able to shoot down a missle, but all of the advances that were funded by the ABL development mean that subsequent generations of DE weapons get developed in progressively shorter amounts of time. The ABL with its COIL laser is arguably the most mature laser weapon and certainly the most powerful at this point. But the nextgen systems like HELLADS will certainly be more compact and efficient (think orders of magnitude) and will take much less time to develop as well. That is why it is important to invest in promising technology even if it will not yield an immediately useful product. Heated debate serves to help determine which technologies are truly "promising" and which are just wastes of resources. But in the case of ABL it seems the US made the right choice and is starting to reap the benefits.