The original recording was produced by Nyman himself and is characterised by the multi-miking, near-saturation and closeness for which performances of his music are generally noted. The DSD (stereo)remastering was done by Simon Heyworth in August '01 and it does sound better than the original. Although there's not noticeably much greater bloom, instrumental definition & tone is clearer and more characteristic of the instruments, especially John Harle's and David Roach's saxes, and that in turn adds to the stereo effect.
It also adds greatly to the "height" of the sound. Fittingly for film music, it now covers a canvass as tall as it is wide. The sometimes electronic-sounding violins of the Munich Philharmonic not only pack a punch, they also soar. Bass extension is good without being dominant, as it can be in many Nyman albums.
The immediacy of the sound is part of Nyman's stylistic signature of resolving the almost opposing forces of hysteria and inevitability. For the "Piano" this conflict is less explicit than in some of his pieces, but no less forceful. The hysteria here is an inward and muted one, befitting its association with the mute, piano-obsessed, emigrant bride Ada. The music too was written to suggest both Ada and her childhood memories of songs and piano pieces and so it reflects "Scottish" type themes and melodies as well as the tempestuousness of the new world Ada finds in New Zealand.
I found the film itself embarrassingly melodramatic and it hasn't grown on me in the decade since its release, but the music has. It is possible to find it lightweight initially, a la George Winston and co, but it holds more than it seems to. It is deliberately "naive" music and eventually works on an almost atavistic emotional level. It's also bloody lovely, with a main theme Paul McCartney would die to have written (as Douglas Adams would have written).
So, to sum up, it was worth trading in the redbook version for, and it'll get regularly played.