I've carried out some testing over the past day or so and am very impressed by the improvement in sound quality
as well as the vastly improved noise floor. A few observations...
playback in VLC 2.2.1 Terry Pratchett (Weatherwax) is excellent from my archive of home-encoded LAME VBR V3 MP3 files.
2/ The same tracks played in gkreidl's Raspbian compile of KODI 15.2 from Dec 14 2015 is equally excellent, although SD and HD video soundtracks warble heavily as though the samplerate is being ramped up and down very quickly. Imagine a cassette player with a badly bent capstan drive shaft and you'll know what I mean. I wondered if this might be due to some kind of audio
resampling going on as I'm watching 25FPS video on a 60Hz panel, but no amount of playing with KODI's audio
settings fixed it, apart from forcing ALSA which brings the noise back again, so I guess this defeats the new sound scheme.
3/ The sound in my own compile of Quake3 Arena is amazing compared to how it was before. Very crisp and clean.
4/ The sound in the Pi version of Quake Darkplaces is completely missing. Checking the console for errors after exiting shows a long stream of S_StaticSound: "ambience/fire.wav" hasn't been precached
(with various filenames) type errors.
Hopefully the above will be seen as bug reporting, not criticism. It's a sonic marvel for the ears to behold compared to how it was when it's working properly. Big thumbs-up!