I have been running the 48" for a couple of months on my wild discus tank (48x24x24), and so far so good. discus enjoy the lower light. I just wish it had two switches. even tho I have a lot of surface aggitation there is no shimmer effect. the light is hung about 8" above the water. all in all, for the price, I'm happy.
I have 2x48" on my 220 hung 12" off the water and they shimmer like crazy, espicially the moonlights!