At first I was a little skeptical of what to expect from this box, considering its price tag was below $100, but now that I've owned it for a while I have been pleasantly surprised. I have never owned anything from Native Instruments either, so I was a little wary of the all-plastic construction. Don't let that, or the price, deter you, this thing sounds great, and it's sturdy and reliable.
I am a semi-professional DJ and producer who's played out of state, and this thing has served me well on sound systems in excess of 100,000 watts. I also just purchased an Apogee Duet 2, and after doing some A/B testing I am hard-pressed to find a dramatic difference in the sound quality of the two units. Compared to the Duet 2, the Audio 2 DJ may be lacking a little high-end detail, slightly less meaty and a tiny bit muddier in the low frequencies, but I feel like it has nice midrange articulation. I think the overall sound stage separation and intelligibility is better in the Duet 2, as well as the dynamic range, but like I said... the differences definitely took some effort to pick out, and they are far from night and day. This could all just as well be in my head, just as all things audio are very subjective.
One thing I would disagree with is the other review I saw in here that says that it drives 600 ohm headphones easily. I have a pair of 600 ohm AKG 240DFs, similar to the other reviewer, and I don't think it has adequate juice to do them justice. 600 ohms is a hard load to drive for a unit that small. It's passable, but not great.
I have never had this thing fail on me, whether from poor audio/USB cable connections, or drivers. This thing has seen countless gigs, including a week at Burning Man, and it has yet to fail me. The volume knobs are starting to get a little staticky - that's probably just the dust from Burning Man that needs to be sprayed/cleaned out!
Overall I am very impressed with this thing, and you absolutely can NOT go wrong for the price!