I've used it many times. The thin fleece is great for a small childs' quilt as it is soooo lightweight (easy to drag around and be loved to tatters) and makes the quilt feel softer. The thicker fleece works nicely, too, and gives the quilt a slightly puffier, softer feel than 'regular' batting.
I've also use the cheap blankets sold by WM for batting. I think that would make a great batting for a utility quilt, too. But it makes the quilt very heavy - and warm.