How does USB 3.0 achieve the extra performance?
USB 3.0 achieves the much higher performance by way of a number of technical changes. Perhaps the most obvious change is an additional physical bus that is added in parallel with the existing USB 2.0 bus.
This means that where USB 2.0 previously had 4 wires (power, ground, and a pair for differential data), USB 3.0 adds 4 more for two pairs of differential signals (receive and transmit) for a combined total of 8 connections in the connectors and cabling. These extra two pairs were necessary to support the SuperSpeed USB target bandwidth requirements, because the two wire differential signals of USB 2.0 were not enough.
Furthermore, the signaling method, while still host-directed, is now asynchronous instead of polling. USB 3.0 utilizes a bi-directional data interface rather than USB 2.0's half-duplex arrangement, where data can only flow in one direction at a time. Without getting into any more technical mumbo jumbo, this all combines to give a ten-fold increase in theoretical bandwidth, and a welcome improvement noticeable by anyone when SuperSpeed USB products hit the market.