I have a K70RGB. The LEDs aren't as bright at full brightness as the Shine III. However, they are still nice and visible during the day, something I struggled with with the Deck keyboard's lighting and their PBT caps. Mind you, I'm using the K70 with the Vortex PBT shine-through caps, which is a testament to how good those Vortex caps are.
I should point out, though, that Corsair have misled with their marketing. The keyboard's advertised as supporting 24.7m colours, when in actual fact it only supports 512. We don't know yet if this is a hardware limitation or a firmware limitation (the latter means it could be fixed).