Doesn't work for me personally - I recently ground up some of my usual oatmeal with a coffee grinder to make it ultra fine (which it did).
But then when I added it to a protein shake it was lumpy as hell and reminded me of these old Weider protein powders back in the day when mixability was not their strong point.
I believe if you can pull it off and choke it down then it's almost the perfect meal but it didn't work for me personally.