Well, I use fleece as backing all the time -- it's soft and warm and cuddly! The better fleece does not pill. I also like that it comes 60 inches wide, so 2 yards of it makes a backing for a nice-sized lap quilt. It's also great for baby blankets.
I have used fleece as backing with batting and without. I like using batting, but thinner batting is best, in my opinion -- like Warm and Natural. It gives the blanket some weight but also some drape.
Hope that helps!