I've been using it and no, I don't plan on freezing my quilt, so it isn't an issue. It will wash out. I just finished a quilt that I had used several things to mark the quilt. Knowing that heat often sets things, I washed the quilt and most of the frixion pen washed out. The rest of the markings I took an iron to.
I do always test the pen prior to using it on my final project. I haven't come across it bleaching anything yet - but I also tend to use med to light color fabrics because dark fabrics are a pain in the butt to mark well.