I agree with the other posters about the fact that the flannel from JA Is thinner than name-brand LQS flannels. This said, at the risk of activating the quilt police, I will admit to using it as a backing. For quilts that I am making to really use, those throws that are in and out of the washer/dryer, I will use JA flannel for that. I actually like that it is a bit thin as it makes for very easy quilting and compared to a thicker LQS flannel, it needs less time in the tumble dryer, thus putting less stress on the top. And it is true that some of these fabrics pill worse than others, but even with the pilling (which changes over time) it is very soft and snuggly.
Being able to back a large throw for about $15 when the flannel is on sale like it is right now is soooo much nicer than spending around $60 for premium 45” wide fabric. So, if the use is appropriate, I will happily use JA flannel. And in all honesty, they have some pretty cool new prints out right now.
Hope this helps.