Serger thread is a finer or thiner thread so when serged the seams are not bulky. Serger thread breaks easier, makes since for it is finer. I personaly wouldn't ever spend time piecing a nice quilt top with it for the seams of some who have used it have come out. As for quilting with it a whole different story. If you have pieced with a good 100% cotton thread and use a good bobbin thread you might get away with quilting with it... As one of the ladies here said I also love to quilt with Varigated threads. I prefer the blendables not varigated. They are by Sulky of America. I love the 12 wt threads.
The better the threads the less wear on your machine. If you hold up most serger threads you will see how fuzzy it is.
ConnieF