Right now, FPGA miners are more efficient than GPU miners and use much less power, but only a few perform significantly better at hashing than the less expensive GPUs.  It comes down to how much you pay for electricity vs. how profitable you can mine with an FPGA.

I'm confident that ASICs will ship...eventually.  And once they come on line, then the FPGA miners will be no more profitable than the GPU miners.  I'm patient enough to wait it out.