Hi timm,
Here's my try.
To my ears, it's a very easy to listen to CDP that is quick, transparent, robust, engaging and tonally even handed. It fleshes out the sound stage quite well (imaging and dimensionality are quite good IMHO) and it's very easy for me to hear the recording venue ambience including the classical and opera stations on XM. To me, that's a great indicator of the "character" of the unit.
The Esoteric K01 clearly did some things better but, as I said before, I wasn't able to emotionally connect with the music like I can with the 306. Read, the K01 was more precise in some ways but more "mechanical" in it's overall presentation.
Regarding your last question, I would assume their DAC's are voiced in the same manner but I've never heard them so that is pure speculation. All things being equal, one would assume they are better than the DAC in the 306. Regarding voicing, I'm a big CJ fan and I really like their "house" sound given the fact that I'm on my third CJ preamp. I think the same holds true for Cary.
And in the end, your reaction to the 306, the K01, the OPPO 105D, and all the other optical disc players out there may be entirely different due to your personal biases, listening room, equipment, type of music played, etc. What's interesting is that Michael Fremmer / Stereophile reviewed the original unit as well as the updated version and he really likes the sound. Of course, it's no longer being built but it's pretty easy for me to get a handle on the sound of other disc players when he reviews the competition. As you may know, he's a huge analog fan and generally does not give positive reviews on digital playback systems.
Perhaps Joey and now Dave can chime in with their observations since they both own the 306. I, for one, would be most curious.
Hope that helps.
Best,
Gordon
PS: Recently had a chance to pick up a used Playback Design MPS5 at a really good price. Decided not to pursue. Also, when they show up on Audiogon, they seem to sell fairly quickly. Not too bad for a "dated" piece of digital gear.