My Husquvarna Viking Designer I sews just fine with cotton thread, but the minute I try to free motion quilt with cotton thread on that machine, I end up with mess. It loves rayon thread for free motion. My babylock loves all threads. Yes, I think each and every machine has it's own quirks -- you just have to figure out what it is and then baby that machine. With all the decorative threads available to us now, I think the rule cotton with cotton no longer applies.