I had a singer for 25 yrs and now my daughter owns it, I have a Kenmore/Janome and a Viking Ruby and a Mega quilter. The only thing the Viking dealer told me is that Viking recommends the Aurifil in the mega quilter but I was never discouraged from using any thread. I've used them all and even more so now that I'm into embroidery. I had one issue embroidering w/serger thread and researched until I found a possible problem and that fixed that. For what I was doing I had to double up on the stabilizer and go up in the needle size; no more thread breakage. I've had a spool of thread that I'd used before all of sudden act up; I take if from the top of my machine and put it in a coffee cup and it's very happy. I don't have any threads that my machine doesn't take and take well. I do think some times you might have to figure out a better position or needles or something to make it work but I've never failed but truth be told, I've had very little trouble with any threads in any of my machines. I agree, who would want a machine if you had to only use one thread; what happens is that co goes out of business. Life is too short to have a machine spazing over something as simple as thread.