The real limiting factor of contemporary and future computing systems (from desktop to high performance ones) is power. The FPGA can give GPU and (especially!!

The real limiting factor of contemporary and future computing systems (from desktop to high performance ones) is power. The FPGA can give GPU and (especially!!) CPU a run for their money in the area of performance per watt. The clock frequency gap is not relevant at all. It exists here as a side effect of some old wars between vendors. Some of recent CPU projects for exascale computing specifically reduce CPU frequency, trading it for predictability and reduced latency of operations. Both amount in less wasted cycles and in greater efficiency in the end. Witness Xeon Phi, for example. As for embedded devices... I don't know. My friends from embedded world used small FPGAs as a replacement for a lot of standalone logic chips (FPGA reduces set of 74xx chips to one). That's about it.