I usually use a sold back, because thats how my Mom taught me, Ha ha. Old habits.
I've been doing a lot of baby quilts latley (I dont know but all my friends are expecting!) and I've been doing traditional cotton designs on the front and using flannel for the backing so it will be extra soft. I'm sure there's someone who would disapprove of mixing the fabrics, but the new Mom's seem thrilled that it's soft.