For a more extensive written review (while having problems getting the videos loaded) see Janome Free Motion Couching Foot Review Part 2.
I decided to test this yarn on my free motion couching foot that I adapted (hacked) from the convertible free motion quilting foot set by Janome.
Here's the final video in the review of this foot.
In the end, with a larger diameter yarn this foot did much better. As I said in the video, I'd like some changes in the foot, but it enlarges my toolbox (of techniques) and so I like it.