Satfrat's advice is about the best I could give to anyone thinking about trying higher end USB cables..."If you're not willing to spend, don't try these cables out". If you buy one of them, you'll likely keep it.
The Poiema is a great cable and the improvement is on par with changing a source component like a DAC (in comparison to the Cryoparts or Belkin cables). They definitely do take a long, long time to settle down though, and the frequency emphasis shifts around during break-in/settling. That's been the case with every USB cable I've tried.
I give Robert at RSAD a hearty reccomendation as he's a fair guy to deal with and customer service was well above average. Can't comment on Locus other than the Cryoparts cable, which was great in it's own right. I do like the Poiema for it's laid back attributes, it's definitely more polite while giving you plenty of detail and dimension.