Have had the SL-D usb cable in my system for nearly three weeks and have to say it is head and shoulders above any other usb cable I have owned, and the most expensive. That being said I find it worth every penny for the improvements gained. Real heft and texture to the lows, gorgeous open mids, highs sparkle. Each sound has an energy that I haven't heard before along with layering and the increased depth of stage are stand out points.
Paul only sent the SL-D and a set of his B42 interconnects to compare with my current cables as I have bought from him previously and ended up buying the lot. Majorly impressed, didn't expect such a system boost especially from a usb cable!