This topic seems to always have folks on both extremes but rarely in the middle. I do find that most who claim they can't hear a difference more than likely don't have stereos resolving enough to show a difference in the first place. However, this isn't always true.
I personally, along with a handful of others have done extensive blind testing of many USB cables at a local audio meeting and we all agreed that we heard not only differences, but improvements in sound. This ranged from cables that come stock with printers to $1k+ cables where all the conductors are held separately from each other in a ladder pattern, and everywhere in between. I believe there were 14 cables in total during this test and we eventually pit the very best together and the best we all agreed upon was the AudioQuest Carbon 1m.
There's no reason why any USB cables should sound different from each other, being the digital nature of this cable. But the truth is, they do sound different. Naysayers can cry all they want, crap on threads, ask for lab data, etc. but until they have heard it in a capable system worthy of revealing the differences there's no real point in arguing.