To put it simply, UASP throws on top a blanket of modernity to the USB transfer protocol. USB 2.0 and 3.0 at the moment still rely on the Bulk-Only Transport (BOT) protocol for mass storage I/O, which is a very simple (a nicer way of saying dumb) protocol that limits USB 2.0 to just 480Mbps, while USB 3.0 carries a maximum data rate of 4.8Gbps – hence pushing the limits of the BOT protocol, especially when one is moving 100s of MBs per second from an SSD or a VelociRaptor.
UASP will ditch BOT and have something similar to SCSI as a replacement, making it far more suitable for low-latency bulk data transfers. Hot Hardware did perform a benchmark, hitting 5% to 20% increase in speed boost compared to the 70% that Asus claims. Minimal? Well, at least is better than nothing, right?