I have one. I like it.
Things do sound better. That is EVERYTHING. Has nothing to do with bit rate or sampling - WMA encoded at 128 bit variable, MP3 at the same, and high res all sound fantastic.
Is it a device for everyone? Nope.
And I call BS on both the Pono Store and HD Tracks. Neither sits and transfers the masters. They just take what the industry gives them. Complete with no dynamic range. In the case of older albums, if you look at the audio in Audition, the most you see in the upper, magical range, is noise. There's rarely, if ever, any actual music data in those higher ranges. 44.1 seems to be the real cut off in these cases. Sometimes on newer albums you'll see if bump a little higher, but never what you'd expect for what you pay.
I rip all my CDs in FLAC these days, and I think I'm perfectly happy with 44.1/16 sound quality. I won't be buying anything from Pono or HD Tracks.