I have a 6 by 2 * 30" at home and I plan to use 8 of the new lights. I currently use 6 Par 38 pendants on a track light and I think this is a better solution for me as I don't have a canopy though I do have an overhang 12" above the tank, but I really have no way to mount most lights. My original intent was to light my tank with Sun Tunnels and they weren't intense enough and sunlight is not consistent, in the winter it is too dim. The main limitation is heat and at this time anything much bigger would get too hot, we want to stick with passive cooling as fans just are noisy and failure prone. I think for most users the practical limit of these lights will be 4 on a 75 gallon. Beyond that, other fixtures become better solutions for price etc, but in my case I don't really have other options, I need to supplement the Sun Tunnels and the magnet mount is ideal. It is probable that in the future we will have a bigger light for bigger tanks, the technology improves rapidly.
There will be a controller that can run up to 4 lights, it will have sunrise, sunset and dimming and with the Reef model LED (blue and white) you can vary the ratio of blue and white.