It sounds really good to me. However, it's the only audio-to-digital converter I've used, so I really have no basis for comparison.
Because there is no level control on either the Seduction or the Linestreamer, and the Linestreamer defeats the level control of the software mixer, I have no control over the level of the recording until it's already recorded and I can normalize it in software (I'm using Audacity). No record yet has come anywhere close to clipping, which is good, but that means I could put more signal in than I am. I would have thought that this would present noise floor issues, because I'm bringing up the noise with the signal when I normalize everything, but it hasn't been a noticeable problem. This is a testament to the low noise of both the Seduction and the Linestreamer.
I mostly us it to make CDs to play in the car, which does not have a very nice sound system, but I am very happy with the quality anyway. The recordings have the great dynamic range of vinyl and a warm tubey sound.
The one thing I've been disappointed with is that the firmware does not get along with Mac Mavericks OS. Not a big deal for me, since I was planning to make my old PC laptop a dedicated audio device anyway, but if you have a new Mac it might be a problem.