OK, to get back to the original topic, here are a few excerpts and paraphrases from what Bob Katz says about using high sample rates in Mastering Audio. (ALL advanced tapers should buy this book!) This is just to get you the flavor, it doesn't do justice to his 6 page discussion of the topic.
"[H]ow can 50-year-old ears detect differences between 44.1 kHz and 96 kHz and even 192 Khz sample rates, even though most of us can't hear much about 15 kHz? I believe the answer lies in the design of digital low-pass filters which are part of the requirements of digital audio. [ . . .] One type of filter has a sharp cutoff; the consequences of sharp filtering include time-smearing of the audio, possible short (millisecond) echos wich are caused by amplitude response ripples in the passband frequency response (20 Hz - 20 kHz), . . . Moving the filter cutoff frequency to 48 kHz (for 96 kHz sampling rate) relaxes the filtering requirement and makes it easier to engineer filters with less ripple in the passband and less phase shift near the upper frequency limit."
To answer my question:
"Moorer [of Sonic Solutions] pointed out that post-processing, such as filtering, equalization, and compression, will result in less distortion in the audible band [at 96 kHz] as the errors are spread over twice the bandwith -- and half of that bandwidth is above 20 kHz."
"In addition . . if after processing the destiantion is DVD-A or SACD, then the master can be left at the higher sample rate and worklength, avoiding another generation of sound-veiling 16-bit dither and yet another sharp filter at the end of the process. Thus, consumers should not scoff at DVDs which have been digitall remastered from original 16/44.1 sources. They will be getting real, audiophile-quality sonic value in their remaserters."
While there would probably be diminishing returns, I [zowie, not Katz] would imagine that the above applied equally to 192 kHz. Katz suggests that 96kHz would perhaps be a minimal sampling rate if there is a redesign in PCM converters to make themer more psychoacoutically correct than they are today.
I would think that higher sampling rate would especially benefit those of us using consumer/prosumer equipment (M-Audio, Edirol, Sony) and software that probably has relatively lower quality digital filters compared to the big dollar rack gear.