I don't use starch in general (even when I had to wear dressy clothes to work I would find outfits that didn't require ironing). Therefore it never occurred to me to starch my quilting fabrics, but it's probably an idea worth trying just to see. That said, there are a lot of things I'd like to try out that I don't get to and I may never do it.
I did use starch once when I was using flannel for a backing. The flannel tends to bunch up and I find tucks at stitching intersections if I'm not very careful. Starching the flannel held it in place and I didn't have to worry about it tucking. It saved a lot of time because I didn't have to hold the fabric taut while I sewed and I didn't have to redo any of the quilting. I wouldn't have thought about using starch if I hadn't read about people doing that, so yay to all the quiltingboard posters!