Here goes (FYI the white balance sucks):
First impression: it's a beautiful set. I got the base + ortho 40 kits. ePBT feels a bit grainy but not as coarse as the KPRepublic DSA PBT set I own. Thickness, they are more or less equal. Legends are sharp & crisp. At a glance I don't see any noticeable warping. Also, seems like there are extra keys: one 1U backspace and 1U Fn (in yellow rectangulars)?
I think my row profiles are all OK.. (Keyboard cherry profile noob here. Would appreciate if someone can help to check).
Don't have chance to test them on a real keyboard - probably weekend.
If one ask me what can be improved, I'd like to see more contrast between the alphas and the modifiers. Perhaps make the alphas slightly brighter, or the modifiers slightly darker. Also, compared to the red & blue accents, the teal/aquamarine looks too bright. But yeah those are kinda nitpicking. All in all, I think it successfully fulfills the original goal of Slate (or Concrete). Good job Hiney for the set!