I've used it a lot- Big Butterfly was free motion thread painted using a lot of Sulky rayon and I also did the quilting using Sulky rayon. Sulky rayon does great for FMQ and is strong enough to hold up to the quilting part. However, I only use it for wall quilts since rayon is sometimes less resistant to abrasion than cotton or polyester. So for a quilt that will be used and washed, etc. I would use something else. Also, I should mention that the smaller sulky spools tend to create some tension issues as they get toward the end, due to the way they are constructed- something about that ribbed plastic seems to grab the thread and keep it from coming off the spool evenly once it starts getting low. So that's something to consider, though there are work-arounds that I've used at times when I really wanted that sheen.
Rob