From my perspective the best thing about PSoC 4 is the fact that it is baed on the smallest and lowest power ARM processor available, the Cortex-M0 processor, which consumes as little as 16µW/MHz (90LP process, minimal configuration) in an area of under 12 K gates. So in addition to the customizable analog and digital fabric of the PSoC, version 4 provides a stop mode consuming only 20 nA (while retaining its ability to wake up) while its low-power retention sleep mode draws only 150 nA without disturbing SRAM data.