I correctly assumed the Metropolitan Opera’s world premiere production of "The Hours" would eventually make its way to PBS. What I didn’t anticipate is how difficult the opera would be to watch. The unflinching depiction of hopeless despair is unbearably grim. I repeatedly paused the three-hour broadcast lest I fall into a sympathetic depression. The three stars- Joyce DiDonato, Renée Fleming and Kelli O’Hara- portray the suicidal gloom devised by Kevin Puts and librettist Greg Pierce, based on a novel by Michael Cunningham and inspired by the work and life of Virginia Woolf, with upsetting fidelity. Everything about “The Hours” is outstanding- and that’s why it’s almost unendurable.