i had great results from HB15, and i use Source Brand Focus HF right now and i'm getting good results with it, and also i am using the keratex hoof hardener. My horse's shoes stay on about 7 weeks this way.
I use Grand Hoof Pellets, Omega Horseshine, durasole and venice turpentine. Over the last two years, there has been such a dramatic, dramatic improvement in my horse's once brittle, shelly and thin-soled feet. Every time my farrier is out, he comments on how he can't believe it's the same horse because he feet are so much better now.
And keep your horse's feet as dry as possible. I make sure I slop on as much turpentine as I can get on his feet before a rain event.
I am having good luck with Biotin 800 Pellets- 50mg on Biotin per oz. All my horses get 1 oz./day, and my one with not so great feet gets 2 oz/day. I also use Durasole. It seems to be helping so far and it's been about 2 months. I also give all mine about 3/4 cup of Omega Horseshine.
I have had amazing results with Smartpak Smarthoof Ultra. My farrier was impressed with the products quality and the price is very good as well. My geldings feet used to be a mess, now they look great!
My favorites, in order of preference:
Grand Hoof Pellets
Uckele Hoof combination
What didn't work for some of my horses:
Different diets and body chemistries produce different results. You may find that changing the base diet may be all you need for great results. Other horses do better with supplements added to their diets and some experimenting may be necessary. One owner on the boards is looking into whether removing the MSM from her horse's diet contributed to her horse's decline in hoof and coat quality. That would be another avenue to look into if you are interested.