I use muslin, when I think it's appropriate. I use it alot when I'm making wall hangings, tablerunners and placemats. I've done some quilt backs with muslin, usually the unbleached as I like the look. I also do backs with patterned fabric that goes with the quilt and binding. A lot of the time I'll take leftovers from the front of the quilt and piece together a strip to go down the middle of the back, or off center, wherever I feel like putting it, and join it with other fabric to make a backer. I think this is a good touch too.