My mother-in-law, Judy, just told me about King Arthur Flours getting into the gf business. She wrote:
"I think that King Arthur has good quality products and have long been on their mailing list. I just got their announcement of a whole line of gluten free products and thought you might be interested in checking out their website."
Their site mentions that they have a dedicated gf facility, so it sounds like they are serious about this.