I've reworked the board for a bit more copper efficiency, and double-checked some suspicious-looking component values.

Also, this will be "version 1" of the Shield; "version 2" will replace the 3.5mm TRRS plug and right-angle headers with a pair of 2.5mm mono audio plugs, for those cases where the mike and speaker go to separate places outside the enclosure for the Arduino boards.

There are a few things I may yet change, such as rotating the 24LC32 counterclockwise; rewiring the audio plug to make it at least nominally compatible with one of the common TRRS standards; or possibly migrating the MAX11312, its surrounding capacitors, and some of the components to "south" in a "northward" direction. Other than that, a tiny bit of trace-juggling, and anything based on input from you, Dear Readers, this is pretty close to ready.

If I upload another update to the layout, it'll probably be the last one... but I've said that before, so no promises.