Just got the StereoLab XV-Ultra today. I have been using the StereoVox XV-2 user for the last few years to feed my PS Audio DLIII (w/Cullen L4 mods) DAC. I was very pleased with the XV-2, and from just initial impressions, and although not fully broken-in, the XV-Ultra has surpassed it. I really liked the XV-2 for it's accuracy and for the amount of detail it was able to pass from my source, and the XV-Ultra knows how to get out of the way and pass along even more detail.
I can post more after a week or so after the cable fully breaks in. I also like that I don't have to pay an arm and a leg for really high quality.