I have a 25g high tank. 55W/10,000k 50/50 PC light. My tank is not very advanced, it's rather basic. I have about 1-1/2" CC, one powerhead and a 330 Penguin BioWheel rounding out my equipment. I have two small clowns, a purple psudo, and a stripped damsel for fish. My bubble tip anemone just died, leaving me with one choclate chip starfish, a Condy, three large snails (and one micro baby snail I found yesterday, but haven't seen since) and two small hermits. Oh yeah, I also have the electric scallop I just bought.
So there is very little bio-load on my system. The PC light is new, I had the standard light on until a few weeks ago. The tank has been up for about 8 months, and with this basic set up has worked well. I put the PC on after reading post after post on site. Prior to that my condy got sucked into the power head and lost 90% of its tenecales. It recovered slowly, but when I put the PC on it's regeneration rate improved at at lease 4x. So I am now a believer in PC lights. Kinda makes me think all the rest of the stuff I read hear has merit also...LOL