I guess we've had our Playback about 2 years now. To me, it's the best sounding, most honest DAC I've heard.
I spent about 2 years trying a bevy of digital converters for mastering. Before I got the PB, I felt the DAD AX24 had the best DAC section made. We've had in here the Berkeley, Prism Dream, dCS 9xx, PM2, Lavry Gold, EMM/Meitner, UA2192, Crane Song Avocet, Dangerous ST, Genex and more I can't remember right now. We still have the AX24, EMM/Meitner and Avocet that we're using every day.
The best thing about the PB is the coherency. From the lowest of lows to the upper frequency extremes, the PB is the most linear of them all. The DAD excells in the mids/upper freq and the EMM/Meitner does great from the mids on down. The PM2 is bottom heavy to me which the Berkely also exhibits that trait. The only downside I see to the PB is that the USB only goes up to 48k. We use the Lynx AES16 via AES/EBU into the PB and it sounds magical. The DAD is very analytical, which is good for picking apart music. The PB will let you hear deep into the music as well but it won't draw attention to itself and it's not fatiguing over extended periods of time unlike the DAD.
The Berkely we felt is musical, but it didn't allow us to hear the low level details needed to make critical adjustments to clients files without second guessing. With the PB, it's the only DAC that I've heard where I can actually sense the size of the venue by the ambience. If I make a .5dB adjustmet at 125Hz on the mastering console, I know it's because the music needed it and not because of a poor DAC design.