I used a "sheet blanket" in one of the first quilts I made. In years to come, I was disappointed that I did that only because of the quilt that I wished it was. As far as being usable, it was great. Another suggestion for batting is to recycle a mattress pad. It gives a bit of loft but it dries easily. If the quilt you are making can become wet such as at a beach or picnic, consider that you want it to dry pretty quickly and not get moldy/mildewy. It may get picked up while wet and forgotten for a time!