Ian was nice enough to send me a new cable and, after a bit of trimming (had to invert the ribbon cable connector on the sensor side) it works perfectly! No complaints other than maybe to QA check the ribbon cables a bit better
The kit is overall 4.5/5!
"I figured out that the problem with the *new* cable was that the ends were crimped on opposite to the proper direction. In other words, one end had its pinout rotated once vs. the proper direction, so the +5V (and all the other stuff, for that matter) wasn't getting to the laser. I trimmed the polarity tab off of the sensor board end with a hobby knife, plugged it in 180 degrees around, and it works fine! Works perfect, actually! The sensors work great, and now I just need to find some free 12 hours to extrude a few pounds of filament
"