I use it for my four, they are all fit and well with lovely coats & hooves. I found my mare a lot calmer on it and less seasonal. Nothing miraculous but definately more calm, however that could also be due to the whole SS high fibre, no added sugar/cereal diet.
I feed it in winter but in summer I feed a lot of brewers yeast and instant linseed so drop the total eclipse. As I feed black sunflower seeds, they get the benefit of the seaweed for the coat and hooves from them.
I feed SS products so the total eclipse is the finishing touch to the diet.
Personally the SS diet works really well for my two and I love the way they are fed - lots and lots of fibre.