My thinking is that it depends on the look you want on your finished project. If you like puffy, then you need a real batt. One of the first quilts I made, I put a flannel sheet inside and I'm now so disappointed that I did that. But that was before I "knew what I was doing" and I didn't have much money then either to put into a quilt. I had put a lot of time into embroidering blocks for a quilt for my little girl and they really deserved better quality for finishing. As with all of our quilt projects, it depends on the use you have for the quilt and whether you want to put a lot of time and money into it. If it's a utility quilt, you may enjoy the blanket inside but, if it's likely to be handed down as a family treasure, you might decide to use the real thing.