They are ofc good if used right, but they wont give you anything food wont, its just a matter of convenience and what you can stomach after a hard session. I know sometimes after a hard run I can barely stomach a drink of water never mind food. I force half a pint of milk as soon as I get home, then another half pint after showering.
Ive been reading some stuff on running by Matt Fitzgerald (Im going to try his Brain Training Plan for running and supplement it with cycling) and he talks about some research into using 4:1 ratio carbohydrate to protein supplements during hard sessions increasing your recovery meaning if you train every day that you will go into the next workout better recovered. But he also details some downsides such as it is good to go into some training sessions in a fatigued state. There is a load of science talk, I dont fully understand this so I wont pretend I do. But its something to think about.
BTW make sure you understand the difference between weight gain formula's, protein supplements and recovery formula's. They all have different ratio's and calorific contents intended for the given purpose. From memory, because I cba to google, isnt Promax a weight gain formulation for body builders?