Take a look at the latest in-depth article added to the site - FPGA-prototyping and ASIC-conversion considerations.
Written by Bob Kirk, of AMI Semiconductor, it covers the best approach for designing with an FPGA...
Depending on the requirements of your system, using FPGAs may not be the best approach for field deployment. Factors such as high unit cost and high power consumption may require deployment with an ASIC device. Still, designing with an FPGA makes more sense, and, by paying attention to a few details up-front, the conversion to an ASIC device need not be difficult. Those details include power supplies, packaging, boundary-scan testing, and other considerations.
Kirk argues that the capacity and capability of modern FPGAs support the implementation of many digital systems, making them "the platforms of choice for developing, prototyping, and deploying digital logic".
FPGA prototyping