Monofilament thread has changed a lot in recent years because people were trying to find a use for it in quilting-mainly to STID around blocks before adding decorative quilting. It was a utility thread. Cotton thread works with the cotton fabric and simply blends into the project. Any of the threads that are not natural fibers will float on your project and lend a decorative look-they do not blend into the fabric as well and that is their intended function. Polyester thread has probably undergone the most change in recent years. However, it is still a petroleum product and will have the same characteristic as it has always had-low heat tolerance. If it does not melt away it will become brittle and break. I would never use rayon thread in anything I wanted to last a long time because it is wood fiber and will deteriorate quite quickly over a period of time-but it is shiny and supple when applied to a quilt. Having a textiles background I would say that the information you get from Superior Threads (Dr. Bob) is very well done and informative. You can rely on it.I realize that he is selling product but I also know that extensive research goes into the products presented. As quilters you choose the quality of fabric and thread you like to use and you get known characteristics from those choices. I personally prefer natural fabrics and threads and I prefer good quality so I won't be disappointed with the result. I like to vary the weights of the threads I use for different looks.