I am on my second grain mill. My first was a heavy duty type Hawo Mill - lovely wooden box and really heavy duty 1/2 horse motor. I used it for several years, but the stone broke and I cannot find a replacement. So, I gave it to my husband to pirate the motor, but the mountings or somehting was non standard so it is useless. So beware a stone mill because the stones break. They are also hard to clean, so if you need gluten free (which I do) you cant use the mill for wheat, etc.
My husband has a severe wheat allergy, so after a few years of no mill I decided to do some research again. After finding out as much as I could and comparing them, I purchased a Nutrimill. I have had it 2 years and it works every time. The other large advantage for me is that it comes apart and is fairly easy to clean, so I can do both gluten and non gluten flours as long as I clean thoroughly in between.
The Nurtimill is a micronizer type mill, which means it basically explodes the grains. Most of the micronizer mills only produce fine flour, but the Nutrimill can make a coarse grind about the texture of corn meal. The only grain I grind coarse is corn, and it makes amazing cornmeal.
I live in Canada and purchased this from Healthy Kitchens in Vancouver. http://healthykitchens.com/aos_online_store.html Carol, the owner, is very knowledgeable, so when I was in the final decision I called her and she had a lot of great information. She has used and sold many brands, and after several years and types she recommends the Nutrimill. The other factor for her was that the company stands behind their product, which she said was not the case for some of the others.
Anyway, I have been very happy. I commonly make bean flours (garbanzo, white bean, fava, lentils), buckwheat, soft and hard wheat, corn, quinoa, amaranth. After you have had freshly ground flour there is no going back - it is really worth doing and saves money. Because of the necessity of using gluten free flours in my household I saved the cost of the machine within a year easily because the whole grains are cheaper, and store longer. I grind enough of each type of flour to last about a month. I keep the flour frozen after grinding, because really flour is perishible.
I consider this an essential kitchen appliance now. It is very noisy, and there is some mess, but overall it is great.