Do a search, people have certainly compared these favorably with Apogee etc. I've only compared them with Lucid, and I prefer it. But in all fairness, I haven't compared just the converter section, so the API preamp would be coloring my opinion of it.
I believe the general consensus a while back was that these converters are equally up with the best for tracking - there might be some color, but it's good color.
No complaints. I do notice huge variation between sampling rates, and I would be intrigued if more expensive converters could sound better at the lower rates. But at the moment I can't tell whether it's my A/D or D/A that is contributing the most to this difference. (Monitoring with a Benchmark DAC-1).
It's just that some experienced people with more expensive converters have indicated that good converters can sound just as good at 44.1 - which surprises me and makes me wonder.
My carbon footprint is bigger than yours.