I have!! Horse was 3/10 lame behind (27 year old TBX ex polo pony). Thought I'd try Devils Claw (the NAF one) as a last ditch attempt before getting the vet out to assess bute/PTS etc. I was amazed! I put her on the loading dose of 100 mls for 3 days, not expecting much, only to find that within 2 days, she was almost completely sound.
This was about a year ago, mid-winter, during the cold snap. She had 5 days in her stable due to the yard being iced up, and went out sound even then.
She now has 25mls daily (quite a high dose, but I'm reluctant to lower it in case she gets worse again). She's leaping around like an idiot on a regular basis and still bucks higher than my head, and rears bolt upright. Completely sound - you'd only notice she wasn't right if lunged on an unlevel surface - and I look at her and wonder why I ever retired her.
I have used this and a buteless stuff (Naff i think) that is the same kind of thing. Horse has Spavin in both hocks, takes about a week from when he looks particularly stiff until you see effects.Works well though. He is 12 so not that old.
My old boy is 31, and I put him on Feedmark's ZeroBute three weeks ago, and there is definately a marked improvement.
He's been retired for 3 years and he's been fed D&H's 16+ Mix and Benevit vitamin sups for years. He's in great condition, but having some shire in him, his heavy joints are really stiff and painfull. This is the first time I've given him anything designed to relieve pain, and everyone at the yard is astonished because he now marches in and out of the field to the stable, as opposed to shuffling, which he was doing before.
I honestly did not expect to be able to see any difference, and am amazed at the difference in him. Literally, last month we were talking about how he was really slowing down, and was I going to have to 'make a decision' soon, but it seems that with the zerobute my old boy has found a tiny bit of sparkle and is enjoying life again.