I have used fleece to back my quilts but when I do, I don't use a batting. I usually use an off white or white.
Also these are usually utility quilts.

I made a quilt last year using fleece for batting. The quilt is very heavy and will be nice and warm. I like to do my own machine quilting - nothing fancy - just meandering and maybe a few names stitched in to it. I had a very difficult time doing a simple stippling. My thread kept breaking after about a foot of stitching. I was too stubborn to stop and just do a stitch in the ditch. When I finished making a mess of my quilt, I then ripped out all the stippling and just did stitch in the ditch. I then washed it to be able to get all the needle marks out of it. I would suggest you try a small sample before committing to the whole quilt.

I dion't much care what the rules are. If I have fleece and I have a personal sized quilt, a kids quilt or a baby quilt-----------I USE THE FLEECE. But I generally use it for the backing. Of course, the quilts I use it on are going to be the daily use and drag around the house variety. If it were a "show" quilt, I'd wait until I had batting.

I used fleece on a backing for my 14 year old grandson and he loves it because it is so warm. I tied it and since I have arthritis in my hands it was very hard for me to get the thread through all three layers.

We use fleece for backing for wheelchair lap robes. They're warm, easy to wash and best of all, they don't slide off your lap. Our nursing home people love them. Also have used fleece for Linus quilt backings.

I use it a lot as batting and backing (just the top and fleece) since it doesn't require the every-four-inches-qulting or whatever, that the batting requires. It washes well and lasts longer than the top. My son's favorite "quilts" are those that are just a great fabric on top and fleece on the back, edges finished by turning the cotton over the fleece edge to self bind, and a few lines of quilting to hold the top to the fleece. QUILT DONE IN RECORD TIME!!!!!!!

The cheap stuff works just fine, too. I've never used it as batting, just backing in quilts with a top and fleece backing.

I used it for batting on my second ever quilt. I used microfiber fabric to make 18 inch squares (what was I thinking?) King size. Three layers, top and bottom microfiber (very stretchy) - fleece for batting. I wrestled it through my dinky mechanical Brother to stitch in the ditch. It was very doable and the quilt came out great. Very warm. It lays heavy on the body. My recepients like that, might not be for everybody. They took it to the commercial laundry and whatever they did to it there didn't harm it. Have not used it with cotton.

I've used it...it works fine but the quilt will not have great drape. Kinda stiff but it works for utility quilts. Just not graceful. Also, it's usually 60" wide and that is a plus. It quilts fine, "not too hot, not too cold. Just right," to quote Goldilocks.

I use polar fleece often for my quilts for my seniors cover ups, top and one layer only.Have been doing it for a couple of years no problems reported I do wash first before quilting.