In USB2 is very correct (20MB in Writing / Playing 30MB)
In USB3 then there is fully exploits its possibilities. On large files, we approach the performance indicated by the manufacturer, for my part on I5 with SSD, I measured 50MB / s write and 180MB / s read. On small files, flow rates decrease significantly, while remaining much better than what can usually be observed for USB sticks.
A product that I highly recommend.