I wanted to test out the structural quality of the models, and decided to start with the simple tree.
Due to several restrictions (mainly because I only had means to print in black and white on plain bond paper) I was resigned to ending up making a big mess out of my first "experiment": I glued my plain paper print to cardboard, then did some coloring, then glued on itself and folded, then cut, then assembled.
Also, I only had cheap (and old) white school glue at hand. I wasn't expecting much, and I didn't try too hard.
Amazingly, the structure still held up firmly enough despite my laziness.
The structures are well-thought, the PDFs are professionally generated, the resolution seems to be adecuate.
I've yet to try actually following the suggestion in the "Beginner's Guide to card modelling" PDF (included). Starting by actually printing directly into cardboard.
This product being free is definitely a smart move by Fat Dragon Games to show the quality of their work.