Till now, I've been a "mix" girl. Adding together all of the gf flours and gums, and making sure I have them on hand, has seemed too complicated. It is more expensive, too, however, so if I decide to stay completely gf, it may be good to learn. During my wheat-free years, we have kept spelt flour and oat flour on hand, so I haven't needed to learn how to use xantham gum or guar gums. My main complaint about mixes so far is that they often use more sugar than I would like.
I asked my neighbor, Tom, a gf baker extraoridnaire, yesterday whether or not he uses mixes. He and Hillary, the master decorator, make their own. He mentioned that bean flours may also not be good for people who get migrane headaches.