I ended up pairing the 9-minute challenge with Tim Anderson's Habitual Strength (doing swings instead of one-legged deadlifts) and I absolutely love it -- it pairs perfectly. Habitual Strength is basically the OS version of your One Lift A Day article.
I wanted to share something I've been doing with your challenge. The part of it that really resonated with me is the part about keeping it easy and relaxed -- this is exactly the way I want to trian because I'm a tense, stressed out kind of guy and my training reflects that.
My first day doing the challenge, I was doing a bunch of stuff waaaaay too hard. For instance, I was carrying the 72lbs KB and by the minute mark, I was working pretty hard and nothing was relaxed. The next work out had me carrying 25lbs dumbbells, and i was completely relaxed as I accumulated 3 minutes. After the workout, I felt nice and energized -- something I'm not used to feeling.
But the light weight bugged me.
So the third workout, I carried the 72lbs KB again, but since I'm able to carry it for 15s in a really relaxed, easy fashion, I alternated 15s carries with 15s rest for six minutes. I was able to stay really relaxed the entire time and still had that energized feeling at the end. Since then I've bumped up to 20s on / 20s off for 6 minutes and am working on reaching an easy 30s on / 30s off for 6 minutes.
I warm-up by skipping rope for 10 minutes, then do this 6-minute-per-exercise scheme for the three moves, so the entire workout takes ~30 minutes. Habitual Strength at night takes 20-25 minutes, with only 10-15 minutes being intense work.