We have been using the Top Spec calmer on a particularly hyper mare - and it really worked wonders. I have always been terribly scepticle about calmers, but can really vouch for this one.
I use Nupafeed on one of mine and have to say yes it does work. Initial costs looks horrendous but the first 5ltr lasts 175 days (you use more for the loading period) then subsequently 5ltrs will last 200 days.
It has definitely helped my horse, he is much less stressed getting ready to go to and at events. He was by no means a headcase but would become quite tense and pooh like a cow! Do think it took a little longer than the 5 days to see an improvement.
Nupafeed is amazing stuff, defienetly the best carmer round, have tried a few of the other well know branded carmers and they didn't make any difference, but as soon as she went onto Nupafeed there was a big difference. We have a few horses on it on our yard and they have all seen a big difference in there horses since switching over to it.
Never tried the calmer, as luckily never needed to, but I used to feed TopSpec balancer which is fab stuff. So if that's anything to go by it should be good!!!!