[DrFalkyn]

They're used in places that require real time processing (DSP) of raw digital signals at very high (several hundred Mhz and more), where you cannot afford to miss a sample because of latency from a microcontroller (uC). I think even some PCI devices use them for this reason, and it allows you to update firmware whereas ASIC doesn't

A while back I wrote an entire FPGA pipeline to recalibrate signals from optical sensors before they were passed on to the CPU. Doing this allowed us to keep up processing speed with acquisition, so it was real time. A lot of FIR filters and FFTs. But my proudest achievement was a linear interpolation algorithm which is fairly high level and tricky to implement on FPGA, which is more geared towards simpler DSP algorithms like FIR filters, and FFT (not simpler but so much effort has got into making IPs it effectively is because you don't have to implement it yourself)

But other than that, for raw bulk compute GPUs are kicking their butts in most domains.