I'm happy with how my first one turned out. The instructions are clear, and they steered me toward a good level of precision.
The layered A0 file went through my projector well. Sometimes I have to edit A0 PDF files to add a blank buffer zone around the edge, so that I can scroll the pattern to where I want it on the cutting table. For the rain hat pattern, I didn't need to do that, because the pieces were already well in from the edges.
The chin strap is tighter than I'd like. I'll probably wear it with the hook-and-loop only overlapping by 2-3cm, not the full 5cm. Another time I'll start with the elastic extra long, and delay attaching the loop piece and trimming the elastic until after a fitting.
I'm not sure I understood exactly where to put the last piece of seam sealing tape, but taping is only an optional extra, and the last piece seems less important than the earlier 5 pieces.