I completed the build and uploaded some pictures of the result. 

It works just fine as it is. There are a couple of things I would do over again if I were to make another one of these. 

Firstly, if I had made the board traces wider, I could have supported a current spec more like 8 amps than 2. I might have also stuck a fuse in somewhere if I were doing it for a wider audience. 

I chose a box much larger than I could have just so I could insure that all the parts stayed sufficiently separated from each other (given that there’s AC line voltage involved). I specifically chose a metal box and grounded it to insure that if anything came loose it would create a ground fault and blow my local GFI (or a circuit breaker). I also chose a nice, big red button for it, but the downside of that was having to grind the hole large enough for it to fit. Grinding the IEC and NEMA outlet holes was a pain too. Of all the parts of a project like this, that’s my least favorite. 

The last little quirk is that when there’s no load at all, the power light glows faintly. When you connect any sort of load this stops, but it indicates some level of leakage in the triac circuit. I probably need to revisit the biasing. But it is “off” enough to keep my desoldering iron cold, so I will call it a “win.”

Lastly, I picked the power supply module I did out of pure laziness. It’s capable of 3W if output, though the 5 volt powered portion of the circuit undoubtedly draws less than 50 mA in practice. I could have bought a smaller one and maybe saved a couple of bucks, at the cost of designing a new EAGLE library entry for it.