There some very nice and pricey flannels out there. I typically don't use flannel because I have pets and it attracts the pet hair like crazy, but I will do donation quilts with it. Actually, the next quilt I will be quilting down has a flannel back. Don't remember the maker, but it is a high quality garment flannel. I'll also be doing the binding with the same flannel as the back, while I know I've done it in the past it is so long ago that I don't remember...
For all flannel my basic advice is wash it at least on medium if not hot with a color catcher so you can see if it is pretty stable or how much dye comes out.