I also have used fleece with no batting on several quilts, and it has worked out fine. I agree that the anti-pill fleece will look nicer longer, and I would also recommend that you avoid stretchy fleece. Check the fleece as it unwinds from the bolt and make sure it is not stretched out in some areas. If it has been wound on the bolt crooked, it seems like it is a losing battle to get it "on grain", especially near the selvage.
Dayle