I found them to be stunning. Incredible speed, resolution, etc. That being said, I also have to admit that I found myself listening to music less and less with them in the system. Looking back, I think they revealed so much information that the mind was constantly looking at all this new information, which led to listener fatigue, at least to me. I found that I got 90% of the resolution with Stealth Dream power cords, but could listen for longer periods of time, the Dreams were a bit more musical.
I'll still say that if I was demo'ing hifi equipment, I'd use the Valhalla cords, as they will really impress folks. I just found that I couldn't live with them long term. YMMV.