Designing DSP hardware is quite different than designing DSP for software based systems. In addition to the obvious considerations for hardware such as clocking, timing and so on, a hardware DSP designer also has to consider how an algorithm is going to map to hardware, as well as the availability of design talent and tools.
Among the things to consider, especially for software people considering an FPGA Design, is that FPGA is fundamentally Hardware Design. While the tools try to hide this fact, ignoring it will lead to poor designs that are bound to disappoint.
Properly executed FPGA designs typically outperform a DSP microprocessor by a factor of 100:1, and by more than 1000:1 in special circumstances
Power dissipation of an FPGA DSP design is typically about 20% of a microprocessor based design working at the same sample rate
Software validation costs are avoided by using hardware
Availability of talent/tools