Not proven in practical combat situations against a first rate opponent- sure, they have shown under ideal test setups to knock down missiles, but one of the liabilities is that a hard kill system could spray nearby friendly troops as well. Furthermore, in a busy combat environment, such a system again could conceivably be overwhelmed by projectiles flying everywhere. In design, they are meant to be one layer of a tiered defense, i.e., in addition to the armor package plus electro-optical jammers and dazzlers, not designed to work on their own per se.