Yes very good. Used it a couple of years ago on my nutty Welsh D and it worked quickly. Using the recommended amount he did turn into a bit of a donkey after a couple of months but when I reduced the dosage he was fine. He's back on it now after a very traumatic loan home disaster and the new loaners are keeping him on it for another tub. With them he's on the recommended dose or just under and they think he's great, just enough sparkle without the silliness.
Im on my 4th week of it and I really think its worked. Hes much less anxious although just the same in every other way. Im going to buy another tub when this runs out. You do have to feed quite a large amount and I didnt think he'd eat it as he is fussy but after sniffing his feed like Id poisonned him for a couple of days hes now fine. It does smell strong though, like brewers yeast.
I have used it for several months for my horse. I have to say I am not sure I noticed a particular difference in his behaviour. I found it hard to assess.