I've used a DA2b for a year or so and have found that the unit is very sensitive to the tubes it uses, but once dialed in will sound wonderful. Also, its very sensitive to jitter, which means that a good transport and digital cable is needed to get the most out of it. Certainly, this shouldn't be an issue with the DV2b, but its something to note about the outboard DAC.
As mentioned previously, the DAC is not the utmost in resolution or speed when compared with others*, but it has a beauty and richness through the midrange that is extraordinarily compelling. The sound will change somewhat depending on which tubes you use, but in all cases the mids remain exemplary. I've used a variety of tubes with the unit and have found a few types that complement it very well. The best so far are NOS Mullards (the type that actually says Mullard on the tube, not the generic British tubes that look similar and are generally regarded as Mullards) and NOS Hitachi. The Mullards produce a soundstage that is incomparable in my system, with a sweetness through the midrange that is simply beautiful. The Hitachis are stronger on the top end and much tighter on the bottom, and produce a far more real sound than Ive experienced with this, or any other DAC. Over the past 6 months or so, these have become my tubes of choice for this unit. The newer, unlabelled variety of Mullards are too laid back through the mids for my tastes, and produce a relatively small soundstage. The original GE tubes (which is what the unit was designed for) provide a pleasant sound, but are unremarkable overall and make the unit seem a little lifeless.
The key difference between the CJ DAC and others Ive tried is the realism of the sound it creates, and its ability to produce and seemingly boundless soundstage when called for. Nearly every other DAC was faster and more accurate, but the emotional impact that the CJ DAC produced with some of my more dramatic classical pieces was never matched by the others. For smaller pieces, however, its lack of speed and accuracy may make it sound a little veiled as pointed out previously.
Anyway, in my environment the upsides outweigh the down, and for that reason I still use it in my system.
* Note that my experience with DACs has been limited to low/moderately priced units (<$700). Keep this in mind when evaluating my comparisons.