I cant tell you much about them personally, but I do know that they can be rather boisterous! Anything really timid that will be using the same areas of the tank might get mauled a bit
long armed shrimp can be very aggressive - depending on what species they are. None of the species should be kept with small fish or fish with long fins. Some eg: Macrobrachium rosenbergii get very large and should be kept by themselves. I would never advise keeping any long armed shrimp with cherry shrimps, if you want to keep you cherrys alive.