A study commissioned by the institute said that decades of experience have proved that the system cannot reconcile the twin goals of individualized decisions about who should be executed and systemic fairness. It added that capital punishment is plagued by racial disparities; is enormously expensive even as many defense lawyers are underpaid and some are incompetent; risks executing innocent people; and is undermined by the politics that come with judicial elections. (source)
This is huge because these are the same folks who, in the 1960's, wrote the "model penal code" and other key documents that became the basis for the various state capital punishment laws. They were the ones that managed to come up with a capital punishment system that could withstand constitutional challenge. But now they are abandoning that effort "in light of the current intractable institutional and structural obstacles to ensuring a minimally adequate system for administering capital punishment" (source).
This probably won't have an immediate effect on the death penalty system, but it is a huge strategic victory for death penalty opponents and gives added strength to the argument that the death penalty is simply unconstitutional. The original codes written after the reinstitution of the death penalty in America in Gregg V. Georgia, 1976 were designed to eliminate the arbitrariness of the old laws, and now that effort is falling apart.
Personally, I don't support the death penalty. I just don't think it squares with Christian ethics. It is state sponsored revenge, and does not prevent further harms any better than life imprisonment. The demonstrable racial and monetary bias (more money=better defense lawyer=less likely execution) just seals the deal in my mind that the death penalty is practically and morally unworkable.