If I remember rightly there was a discussion on this on the Newrider forum. From what I recall most people were really positive about it and were getting really good results.
I work with lots of horses which are difficult to handle, and with young horses, and I can honestly say that every time I tried Pax it made the horse suspicious and prone to take fright.
Perhaps, like perfumes, pax does not suit everyone.
I've got an almost full bottle I could send you if you like.