I think the Pono thing is pretty cool, but mostly because the converters are made by Ayre Acoustics here in Boulder, which will easily blow away the converters on most of the players that most people here will listen to. As far as the format of the files go, I'm not sold. Everyone can find anecdotal evidence where a record sounds better than a CD or this or that format sounds better than another, but 99.9999999999% of the time, this has more to do with the mastering than anything else. The truth is that many tests have been done where people have compared 320kbs mp3s with high resolution audio (88.2k or 96k 24 bit files or higher) and not been able to tell the difference.
I have to say that I love the sound of tape. A well calibrated Studer is an awesome thing of beauty. The sound has depth, impact, detail, all that great stuff (I have some reservations about SR, but that's another conversation. It does provide a more black background, which is very nice). But so does my Metric Halo ULN-8. Even playing a properly mastered CD is an incredible experience through its converters in a good room with good speakers, etc. Every kind of recording system has its positive attributes and its drawbacks (badly calibrated tape machines are completely hideous, as are poorly mastered digital recordings through crappy converters). So, I don't think Pono is really all that revolutionary in terms of the media. If it can inspire the end of the loudness wars and bad mastering, then I think it will be an overall positive thing, but other than that, it seems like dramatic posturing about confirmation bias. With well recorded stuff, delivered on properly prepared media, I don't think one system has inherent superiority over another. We certainly don't need 192khz sampling rates to adequately represent the music. Nyquist proved that a long time ago in terms of the theoretical requirements and people like Dan Lavry showed us that somewhere around 60khz is an optimum sampling rate to represent music with as much resolution as we can perceive. Some systems might sound better at higher resolutions, but that is due more to implementation than it is to an inherent improvement at higher rates. In fact, sometimes higher rates can make things worse. But, implementation is why I have some faith in Pono. Ayre is a great company that makes great audio stuff and with them doing the converters, we're guaranteed that part won't be screwed up. In my experience, it's actually harder to screw up digital sound than analog. Once a design is properly implemented and constructed, it pretty much works. Analog requires maintenance and care to deliver optimum audio over time. Each unit needs precise calibration that can't be built into the system by design.
Here's an article that addresses some of these issues:
http://www.trustmeimascientist.com/2013/02/04/the-science-of-sample-rates-when-higher-is-better-and-when-it-isnt/ One experience I've had is listening to the first playback of the original reels of the master mix from Terrapin Station in 30+ years on a very tricked out tape machine (the whole catalog was being prepped for the Plangent process, which I did not get to experience, as the processing happens later. Here's a circumstance where the digital copy can actually exceed the original analog master) into David Glasser's mastering rig. It was astounding how much depth and detail was in those tapes. And the digital playback sounded indistinguishable to my ears. David's room is capable of incredible resolution, so if there were differences that would carry over to the rigs most of us listen to music on, they would be immediately obvious. Both the tape and the playback immediately drew me into the music and made me forget about what I was listening to. For 90% of us, we can do more for our listening experience by getting good converters and treating our rooms than paying extra high prices for the music we already own. So, I don't think Pono is really necessary.
As far as Bill's point that mp3s vs. CDs are a clear difference, I would imagine that's true in most cases, as most mp3s out there are at 128kbs or maybe 256kbs, but a well converted 320kbs is virtually indistinguishable from CD or higher quality. The key here is the conversion, not the inherent quality of the media. AACs are even better. Put it through average sound system or walkman or a car stereo and there is no hope at all of telling the difference. There is a huuuuuuuuuge discussion about all this at gearslutz.com. It brings out all the various entrenched camps of audio professionals about this.
And as a final note, I have to be skeptical that a 68 year old man who has spent his life in rock and roll has ears that are capable of incredibly fine resolution, especially at higher frequencies. I know I don't.
As always, YMMV.
PS. that Ampex list is legendary in the pro audio circles!