I started using in on my flaxen chestnut Haflinger in about December (after reading your thread, HorseCrazyTeen!). I have definitely seen a difference! She's not completely shedded out, so we'll have to wait, but last year, she was so light, she looked like a darker palomino. This year, she's been on it since her summer coat very first started to come in, and she's stayed a rich bronze color so far. And, for the first time, she had dapples in January! She's kept them up til about a week ago. I ran out, and we didn't get any til a few days ago, so she's been off it for about 2 weeks. Her dapples aren't gone, but they have faded a bit. Now we have it again, so I'll see if they come back.
My friend's palomino varnish roan appaloosa is on it too, starting about the same time; early December, when she first bought her. We don't have any pictures from before, so we'll have to wait til next year, but she has gotten roaner since winter, and her she's getting more spots, instead of just smudging.
My dad gets it at Surplus Outlet. Not sure exactly the price, but he doesn't complain about getting two 4oz bottles "just for the horses", so it must not be too expensive! I feed about 1.5-2 tablespoons per cookie, since our horses are not on grain. My mare absolutely adores them! Paprika treats and carrots are her two favorite foods!