Several notes on audio codecs:
I have not personally encountered a Dolby Digital Plus audio track on a Blu-ray disc, although it is a supported optional audio codec in the BD spec. Some titles that claim this codec (such as "A View From Space With Heavenly Music") are likely misprints copied from the HD DVD version of the title - I have not yet been motivated to add any of these to my Netflix queue to find out for sure. In any case, DD+ (and DTS-HD High Resolution) are largely useless codecs that do not seem likely to have much of a future, since they can easily be substituted with lossless Dolby TrueHD and DTS-HD Master Audio tracks with only a bit more disc space usage.
The actual bit depth of Dolby TrueHD and DTS-HD Master Audio tracks remains somewhat of a mystery at the moment. The physical audio headers for TrueHD tracks do not report the bit depth (unlike MLP, but similarly to AC3). At the moment, their seems to be an empirical trend for tracks with a bitrate under ~3500 kbps to be 16-bit and those with higher bitrates to be 24-bit. However, to complicate matters, there are reports from industry insiders that some TrueHD tracks, such as those on The Fifth Element and Ghost Rider, were actually encoded at 20-bit.
DTS-HD Master Audio tracks do report their bit depths, but somewhat indirectly. The actual reported bit depth is that of the source uncompressed LPCM audio track. Therefore, this does rule out the possibility that a particular DTS-MA track has not been requantized from a 24-bit source into a 16-bit track or vice versa. Basically all US domestic releases with Master Audio tracks are reporting themselves as 24-bit, with 16-bit tracks relegated to European and Asian releases. Making the situation more impenetrable is the fact that there are no open tools at the moment that can convert DTS-MA tracks into their uncompressed LPCM counterparts (which would allow the audio samples to measured to determine the necessary bit depth to fit the data). There are a number of domestic DTS-MA tracks with suspiciously low bitrates which would seem to imply a 16-bit depth.
I had avoided publishing the bitrates for lossless compressed codecs (TrueHD, Master Audio) since they should be considered deceptive numbers and unrelated to audio quality. The bitrate of these two codecs has no relation to audio fidelity, since they are lossless codecs and thus these bitrates only represent the compressibility of the source. However, due to the unresolved issues of bit depth, I have begun adding these numbers to the listings.