FPGAs are awesome. They help solve problems that software is too slow to solve, but aren't large enough in scale for ASICs. They're also great for prototyping new chips before actually shelling out the hundreds of thousands of dollars NRE for a new ASIC design.

Here's a great stackexchange discussion on why and how FPGAs can outperform CPUs for certain tasks: http://electronics.stackexchange.com/questions/101472/how-ca...