The acrylic these cases are made out of is really some of the clearest I've ever seen and had no blemishes or imperfections. It's carefully (and nicely) packaged for shipping, which is good because it's the sort of thing that could get damaged very easily if less care was taken. Assembly is relatively slow to do right, but the process is straightforward and the silicone locking balls, despite some initial skepticism on my part, seem to hold everything in place tightly.
The modularity is REALLY cool. Orca cases fit neatly on top of humpback cases. Covers do not interfere with stackability. Thanks to the anti-skid pads and the way the cases are designed, stacked cases feel incredibly secure. I wouldn't stack them 20 high, nor would I test this stability at a 45-degree angle, but I have no doubt that a reasonable setup would stay intact with kids running around the house and/or small earthquakes.
It is obvious (and the website also makes this clear) that this is a DISPLAY case. If you need to check your army as baggage on a flight... use something else. My guess is that one good drop would break the case, although it would probably protect the models fairly well that one time. It is definitely not for harsh or abusive environments but, as a display/light-duty protection/dust solution it is hands-down the best I've ever seen in terms of hobby usefulness, design, quality, and looks.
I ordered a couple layout layers as well and love them. It seems like such a simple concept and I'm frankly amazed nothing like this existed 20 years ago, but I'm glad it does now.
As with anything that involves working with acrylic sheet, the biggest pieces of advice I have are:
1. Do NOT drop panels while assembling. I didn't drop any panels from this set, but I've done it with other things and acrylic doesn't handle impact with wood or tile floors very well.
2. Apply pressure evenly. I worked each panel into place over the locking balls in several steps, starting from the inside and working my way out. Acrylic sheet has a bit of flex in it, but when it snaps it does so very suddenly.
3. Schedule your manicure for AFTER your build day. Taking the protective film off acrylic always makes at least one of your thumbnails look pretty rough (if there's a tool for this, I haven't found it).
4. Speaking from experience, when you install your layout layers, wipe the bottom of the layer and the case itself, then QUICKLY put the layer in. If you break for lunch and a stray dog hair gets underneath the unsecured layout layer and you don't notice it, you have to take the case apart to get it out. On the plus side, I'm confident that, once assembled, it will be difficult for stray dog hairs to work their way under the layers.