This afternoon's mail included my sample boards (a batch of 5) from PCBWay, and I'm very happy with their work:

Again, this is a somewhat earlier version of the board; most of the components have been shuffled around, and some have been deleted (and a couple added) since I sent this design. This is mostly to confirm that I got the placement of the Arduino headers correctly -- which, somehow, I did... though I plan to recheck and re-recheck it just to make extra sure.

Now, over the next couple of weeks, I'll be preparing the Gerber and Centroid files for an actual (hopefully) working prototype based on the current layout.

And, by the time that arrives, I hope to have other parts of my larger project working as well.