Nick, things are looking pretty damn good there, kudos!
I used a drum sander only once, a painting/slight remodeling job where I had to also re-finish their floor. After renting the machine, I found a floor guy who was doing the same elsewhere and he was nice enough to say "Watch closely." I did, soaking up his technique like a sponge.
Back to my job, I sanded the floor and it turned out pretty good, though I was a nervous wreck from so much concentration. After finishing it looked like glass. Had to use a Makita orbital sander in spots prior.
Plumbing and electrical! Forget it! I'll pick up the phone instead! :)