well I've only owned a horse for 6mths but ever since I started feeding George Baileys lo-cal he has looked a treat and lots of people comment on how shiny his coat is, and last time the farrier said his feet had improved.
Another vote for Bailey's Lo-cal, gives my fattie everything she needs and i add straight oats for a kick up the backside!
D & H Suregrow has also be good for the filly.
My YO swears by Spillers Happy Hoof, she says she hasn't found a horse yet that doesn't like it. I haven't yet found something I swear by, but I know a few people who absolutely love TopSpec products and I'm switching my horse onto it next week after I have a chat to the TopSpec people at Your Horse on Saturday!