I had half a bag of P Concentrate of a friend a couple of years back as her horse broke his pedal bone - it sent my lad doolally (was cantering solid for 15 mins each time I rode to get any sense out of him!) and he is the most laid back horse ever - I've tried everything on the market previously to pep him up a bit!
I used the ERS pellets up until a year ago, they really helped build my mare up as when I bought her she was very poor - black and white mare in signature. I used them as she seems to be sensitive to cereals, she gets really hot and itchy on things like barley. She was also incredibly chilled on them, she had always been quite nervy, wouldn't stand still at junctions etc, and after moving her on to the ERS pellets she chilled right out - I am not sure if it was the ERS pellets or taking her off the cereals. I only took her off them as she doesnt need to gain any more weight, she just gets a small feed of fibre nuts and chaff with her joint supplement and ad lib hay.
Yeah, I've used the Performace Conc, it was to try keep weight on him over winter and pep him up a bit, he was soooooo laid back. It kept the weight on him nicely, but didn't really give him that much more energy, even with some tiger oats added in. In fact nothing really gave him much more energy!