A better frame for the Americans' concoction may be the staging Menotti did at Spoleto, where the piece was sung in Italian and set in an upstate NY house not unlike their own. Emotionally, melodically forward and as a whole short on rhythmic contrast and impulse, Barber's opera sounds like a late transplant of verisimo despite its less naturalistic setting. The libretto's theme -- noncommunication -- is a near opposite thing, but the relentlessness of story advancement makes theme's felt effect substantially less. There is no room left, neither in surface nor sense, for the fruitful contrasts of, say, Pelleas. (From which we learn, to no surprise, that Menotti was no Maeterlinck...)
In other words, qualities that make the piece work so well in excerpt also make unrelieved hours of it rather hard to take -- at least for me. Your milage may vary.
The cast sang well enough Thursday, but it was no accident that the night's biggest hand went to baritone Richard Stilwell. Only he, in the supporting part of the Doctor, bestowed on his character the divine spark of spirit that Menotti could not.