What has been really striking to me is how the sound quality of the MK2 Perfect Wave DAC depends so substantially on the firmware used. With an SD card reader, it is quite easy to demo the three versions of the DAC firmware that PS Audio has made available on its forum. Buy a $5 SD card reader at Radio Shack and you can try each version very easily.
Today, I installed and listened to all three firmware versions in succession for about 45 minutes each (with the PW Transport as my sourcee), starting with firmware version 2.1.0. This is the firmware that is shipping with the latest upgrade kits and is factory installed on new MK2 DACs. With 2.1.0, the sound quality is very dynamic and very extended. However, the upper frequencies seem much too forward for my tastes, making the DAC seem somewhat artificial and ultimately fatiguing. The best aspect of 2.1.0 is that bass is really impressive. It is very deep, very resolved, and moves a lot of air. If downstream equipment is fairly warm and you are looking for better bass, this firmware might be a good choice.
I also tried version 2.0.3 today. This version is supposedly similar to version 2.0.2, although 2.0.3 corrects some minor programming issue that affects the S/PDIF input. (I have used the S/PDIF input with all three firmware versions without any difficulty.) Version 2.0.3 is less fatiguing than version 2.1.0, but bass seems overly lean to me. This firmware might work best if you have a powered sub.
Version 2.0.2 in my system still sounds head and shoulders better than the other versions. The mid-range is simply transfixing and the bass is still really solid -- perhaps not as resolved as with version 2.1.0, but still really dynamic and pleasing. With version 2.0.2, everything falls into place so coherently and musically that I stop thinking about equipment altogether and just listen to the music. Vocals really shine with 2.0.2. Image placement also seems better with this firmware.
So, experimentation with firmware (if possible) is definitely worth the effort.
I dare say that opinions of this Perfect Wave DAC in both reviews and in some DAC shootouts I have read about on other forums are probably not very meaningful. I would not like the DAC very much, especially in light of the price, if it was loaded with version 2.1.0 or even version 2.0.3. With version 2.0.2, my guess is that it would beat all comers in the general price range. (I also question the validity of DAC shootouts and reviews when owners compare the Perfect Wave DAC to Weiss, Berkeley, or AMR, using a computer as a source. The Perfect Wave DAC was not designed as a USB DAC. The Perfect Wave DAC has a special synergy with the Perfect Wave Transport, with sound quality leagues better than from other digital sources, including computers, cheap transports, and even PS Audio's Bridge.)