Started feeding it about 6 weeks ago. I replaced the grain portion of my mare's meals with it. She gets 2lbs alfalfa pellets, 2 lbs beet pulp pellets, 1 lb of Renew Gold and a scoop of vitamins per day in addition to free choice grass hay, decent grass pasture, and 1/2 flake of alfalfa.
I haven't noticed any major changes, but it saves me about $.75/day over the grain I was feeding. She may be (very slightly) less spooky on it as well. So far she hasn't dropped weight and hasn't had a negative attitude change, so I'm going to stay with it for a while.
Never approach a bull from the front, a horse from the rear or a fool from any direction.