Bought this interface to add some warmth and character to my vocals and to add a little bit of tube breakup to my guitar before amp emulation on my DAW. As a preamp it works ok, but the a-d converters cause some loss in quality. I swapped out the stock tube and there was a big improvement.
For electric guitar: the breakup is not a substitute for a good tube amp, but I find it complements my guitar's natural character beautifully. I'm very pleased with the results.
There are a variety of different pre-amp modes, but I'm not really sure I can hear any significant difference between them. The LED peak meter on the top of the device is GREAT, and that together with the -20dB pad renders the limiter functions a bit useless.
Bottom line, Beringer would have done better to invest in the preamp components rather than trying to expand to USB functionality. Without a dedicated driver or proper converters, it's still a decent, cheap tube preamp.