So I've been able to spend some time with the Cyan puck, and here are my initial thoughts. I run the "Ultra Blue" setting on my Gold pucks, and am running the "Ultra Blue" setting on the Cyan as well, so that's what I'm basing my comments on.
1. The blue of the Cyan puck appears to be "crisper". It's hard to explain, but the added green in the tank makes things look a little brighter, even running at the same total PAR as before. It helps water down the Windex look, if that makes sense. There is no green tint. Just a brighter blue.
2. Since you can use more of the light (run more channels at higher intensities) with the Cyan puck running the "Ultra Blue" setting, you have a little more power/PAR headroom with the Cyan puck. The same would hold true with the Optimized III color ratio, but it uses most of the light at max anyway.
3. I am running the Cyan puck on a nano anemone tank, and the added Cyan is bringing out some flecks of red color on a few of my Rock Flower Anemones that I haven't seen before. I knew that it would highlight some colors more (some greens and reds) in coral, but I was a bit surprised at the RFAs. Otherwise, everything looks mostly the same as under the Gold puck.
4. One thing that made me apprehensive about the Cyan puck initially is the changes to the white channel moving from Gold to Cyan. There are only so many LEDs in the light, so the addition of the cyan LED meant that the "warm white" LEDs of the Gold pucks had to go. I *LOVE* the warm/cool white combination of the Gold pucks. It's probably the best color representation I've seen in a reef LED... if you like to run a lot of white... but I don't run a lot of white, so it's a tradeoff I'm willing to make for all the other benefits. I don't mean to say that the white looks bad, it's just not as nice as the Gold puck.
So, after seeing one in person, now I plan to order 6 more Cyan pucks for the Hydra 26HDs that I am putting on the new tank. For my needs, the Cyan puck checks all the boxes.