I can understand why people react so aversely to this film, but, in Birth's defence, it's quite a demanding a piece for it to suit everyone's tastes.
Granted, the plot is slightly unpalatable, and yes, there are instances when the film appears to veer into senslessness, but, unless you want a clear-cut resolution, this cannot quite be written off as shoddy work on the part of anyone involved. Most of the complaints made about Birth have come from people who cannot get past the plot elements of the film, namely, the flirtation with pedophilia. It is uncomfortable, quite so, but that precisely is the point... Moreover, it's worth noting that the characters themselves find it repelling, and that there is nary a sexual undercurrent between Sean and Anna.
I believe one could argue, very strongly, that this plot device is merely a catalyst to throw Anna's psyche into relief. In the end, whether the boy is Sean or not proves irrelevant; the film is less about a bizarre happening than about the extreme psychological test it brings about. It's intense analysis of love, grief, need and the leaps of faith...
Given this set-up, the execution is flawless. What the screenplay does, quite beautifully, is convey silent emotions; it understands, better than most films, that communication is often non-verbal, and in this situation, when the very thing at stake is reason, it is logical that the characters would be at a loss for words. If any given person were to be in Anna's situation...what would they do? How would you react if someone close to you were living through this?
Jonathan Glazer's direction is splendid, building up a somber, airless mood and coaxing superlative performances out of the entire cast. Kidman's performance is somewhat mannered, yet she completely, effortlessly inhabits a difficult role; it is a brave, piercing, bravura performance. She captures Anna's desperation and fragility, but also her privileged lifestyle and upbringing, and the mad undercurrents grief has brought about. The so-called opera scene will be, years from now, considered a seminal moment in her career. Bright is chillingly effective, registering an intensity that is somewhat unsettling, and the supporting turns--which, with limited material flesh out characters, build histories and express emotions that the screenplay only implies--are sterling, especially in the case of Bacall and Howard.
Technically, the film is a marvel. Two things are worth noting: Harris Savides' wonderful cinematography (there are at least three iconic sequences in the film), which creates a look and a mood that is at once foreboding and exquisitely beautiful, and Alexandre Desplat's splendid score, which underscores the drama without becoming obtrusive and blends symphonic melodies with a hi-lo undercurrent that creates an odd womb-like effect.
Lovely, heartbreaking, unforgettable.