I have backed one quilt with a sheet... and it's my absolute FAVORITE EVER IN THE WHOLE WIDE WORLD!!
I take it with me when I travel to the beach or to visit relatives (because I am always cold), or when I have a long car trip where I am not the driver (again, AC makes me cold!), and it has held up VERY well under a lot of pressure for three years. I hand-quilted it, but it was an old sheet of my husband's (I finished the quilt JUST before we got married) and well-worn. I love it, and highly recommend finding one that is "broken-in". I had no problems hand-quilting it at all, either.
Love it. :D