We've been stockpiling nukes for a half-century, and only ever used two. I would contend that the two which were used were a net benefit in terms of what it would have cost (in both American and Japanese lives) to invade the islands.
Of course, the threat is only good if the nation doing the threatening is willing to use it, so the merits of stockpiling are still arguable. With that said, they were something of a tool for a while. It has been argued that Wilson lacked foresight due to his decision to drop nukes, but what would you have done? Would you have been willing to condemn a half-million young American men to die, given the choice?
It's the classic argument, debated since the time of Pericles: is a javelin gone astray responsible for a death?