I've owned a Nutrimill for 2 years. The first year I used it for grinding spelt exclusively, and was THRILLED with the pastry-fine flour it produced.
Recently I switched to hard white spring wheat (from Montana, the "Prairie Gold" chemical-free variety). Even on the highest setting the flour has a bit of a sandy feel, almost like cornmeal.
Alarmed, I called their customer service. Learned some very interesting things about the differences between grains. The Nutrimill is not like a stone grinder (which uses friction). The Nutrimill uses pressure to "explode" grains which is how it is able to grind without exposing the flour to much heat (stays below 118*F apparently). So you cannot pour flour back into the hopper to grind it a second time (and it can't grind rolled oats).
This also means oilier grains (like wheat and brown rice) won't grind as finely as store-bought flours. But less-oily grains (like spelt, kamut, teff and white rice) will grind very fine and silky like store-bought flour.
Just thought you ladies would like to know :)
People ask about noise level. Running the Nutrimill is comparable to running a vacuum. It doesn't bother me but I wouldn't grind grain after the kids are in bed.
I also like that the Nutrimill is maintenance-free. After it finishes grinding, you just wait 5 seconds before turning it off. That blows the dust out of the works. The customer service guy said if I'm concerned about it, I can occasionally grind 3 cups of white rice. Its fine particles blow through and give it a clean sweep. Otherwise, just tap accumulated flour out of the filter now and then (it's a circle of foam mesh).