Pros: Nice metal case, responsive customer support
Cons: Poor channel balance, output impedance is too high for many headphones, poor measured distortion, too much gain for most people
I just completed a full review of the uDAC-2 with measurements on my personal blog. Some of the results were bad enough I contacted NuForce before publishing my review to make sure I didn't have a bad DAC. They verified my results and confirmed my uDAC-2 was "within spec". At their request, I've included their comments in my review.
I plan to be testing other similarly priced USB DACs in the future, but based on what I know about the uDAC-2, I can't recommend it. Even the $29 Behringer UCA202 seriously outperforms the uDAC-2 in most areas.