I used it on my pony as a last resort, without success. Unless it's changed what it actually "says on the tin" is that it has been proven 95% successful in preventing cases of cereal induced laminitis.
It has not been proven to work on horses that are susceptible to grass laminitis.
It will do nothing for equines suffering from Cushings or Metabolic syndrome.
Sorry if that's not what you wanted to hear.
Has your vet suggested it, or have you just seen it somewhere?
Mine used to be on it at vet's suggestion but he did get quite a dangerous impaction (it can cause constipation/slow the gut down) so took him off it. Better to 'manage' the horse correctly imo and it's very expensive in the UK.