as Olga said, the Processing matters Greatly.

I would add that the base ingredient matters as well.

Almonds for instance, are high in Omega 6, easily oxidized, and arguably bad in large doses. as much as many of you love your almond flour, im not a big fan. I believe it to be inflammatory.

some flours such as coconut are simply fiber. not friendly on your intestine, but ok in small doses.

some like rice flour are devoid of nutrients, simply a base glucose. a source of empty calories. I consider rice flour a "safe cheat"

Fruit flours I would imagine too much fructose.

of the above, id say shoot for the sweet potato flour. It stands a reasonable chance of still having some nutrients in it, without all the negatives. And I believe sweet potatoes to be a great source of whole food. The flour if processed properly slightly less so.

I may be wrong here, but I think that the tricky thing with all alternative flours is knowing what processing goes into its creation. I'd particularly want to be careful of any additives or nutrient depletion that go into the process. Almond flour can be made by just grinding up almonds. I'm somehow doubtful that plantain flour or sweet potato flour are that easy and pure to make.

If you want variety, some paleo/primal baking can be done without flour at all, like this recipe I recently made for the holidays: Almond Butter Pumpkin Blondies.

mesquite flour is super tasty, and really, you have to be the source. I don't find it available commercially.

I would say it should be the best of the ones mentioned.

Since mesquite flour is not made from the seed, but actually the pith, it won't have some of the grain issues.

Some of harusame noodles are made from potato starch (others are made from mung beans). I've been trying to find the potato based ones so I could read more of the ingredient listing. The Japanese have a lot of interesting foods made with less common ingredients. Some of these less offensive sources make for good cheats where you can get a bit of taste without causing too much damage.

All of these are available from Barry's Farm.

The only reasonably priced paleo flours that I saw were Coconut and Tapioca.

Coconut is good for crusts or anything that's 'crumbly'. It's ok but too much fiber, IMO. My real fascination is with Tapioca. Works perfectly for crepes and other types of pancakes, which are some of my favorite junk foods. In fact, Tapioca seems to work for just about anything with little need for recipe adaptation.

Have not noticed sweet potato flour anywhere. Given Cordain's recent take on bananas/plantains in autoimmunity I'm having doubts about the plantain crisps and flours...

Lets not forget chestnut flower!