I have three of these (one main, and two linking modules, for a total of 12W) over a 10 gallon reef as the sole source of light. Keeping corals in 10 gallons was once a major challenge. To get enough light, you had to trade for heat, and chilling a 10G was never practical. These keep a variety of soft corals living (going on two years under these, its not a fluke) and don't add significant heat. They do give off some heat, but far less than any other lighting solution. I first tried a single one of these (4W) over a 5 gallon, and even had some fairly remarkable success there, but at 1.2 watt per gallon the results are fantastic. I have not just experienced survival, but have experienced significant growth (my GSP has taken over a rock, from a dime sized frag, like it would in a halide lit tank) and have have had my yuma ricordia multiply from one head to three.
While lighting a large tank with a whole lot of these isn't terribly practical (there are other led options at a bit less $ per watt) due to cost, there is no reason not to try one (or some) of these in a smaller rig.
My only concern with a large tank install would be total light penetration. Right now I'm having really great results, but with only 12 inches of saltwater penetration its fairly easy to get good light all the way through. On a larger (deeper) tank, light penetration is always a concern. Hopefully someone will beat me to it and test these over time as the primary light on a deeper tank.