I LOVE flannel! That said, I will say that I'm kind of a flannel snob in that I only use quilt shop quality flannels like Moda. I probably have as much flannel in my stash as I do cottons. I make a lot of large (almost twin sized) throw-sized quilts and love them because they're so soft and cuddly. I live in CO, so it can be cool at times year round. I love flannel for baby quilts, too.
The cheaper flannels, however, are too thin and are hard to sew with which I learned the hard way a number of years ago when I bought yards and yards of some cheap sale flannel at Joanns. If you want to use flannels, I'd suggest investing in good quality flannel.