I thought hard about these for my 400g but was concerned about coverage in the tank since my tank is 36" deep. The fixture is very narrow so I was worried about coverage. Most cheaper LED's tend to come out like a beam. I think on a standard 18" deep tank, you might be ok but honestly I haven't seen them in action yet. Maybe IPU will have them on display at some point.
Oh and prior to BCA's servers imploding, I think there was a thread about this and a member had acquired some for his tank. I can't remember who!