The singers on this recording are Helen Donath (the governess), Robert Tear (Quint), Ava June (Mrs. Grose), Heather Harper (Miss Jessel), and Lilian Watson (Flora). The role of Miles is sung by Michael Ginn, a boy soprano. The singing roles of Miles and Flora would have been better done switched around, since Ginn sounds too young for the actor playing Miles, and Watson sound overly mature for Flora. The Czech actors are admirably suited: Quint is intense and mocking, Mrs. Grose is befuddled, and the governess is pretty and naive. Weigl is too enamoured of beautiful people sometimes to the detriment of his film and the opera. Here though he's made good choices.
I don't recall the details of Henry James's short story very well, but I don't think the ghosts ever spoke to the living or to each other. Myfanwy Piper's libretto removes James's carefully-crafted ambiguity by having them appear and speak onstage (so to speak). This eliminates the possibility that the governess was imagining the entire business, and layers of complex meaning are collapsed into a simple ghost story. Also, in the prologue, Weigl makes explict the sexual undertones that James only hinted at.
It's a good film, and it should have been on DVD before his disasterous interpretation of 'Winterreisse'