Instead of being sedated and glued to the hive's walls, they run freely, acting in a zombie like state and attacking nearby intruders. If a Predator is infected, it will became insane and attack even its own kind.
In the Aliens arcade, the infectoids could shoot turrets and other guns as well as fight with knifes and metal pipes in AVP arcade. The infectoids were shown to have a blue skin coloration, this may be because the skin has turned pale, such as what happens to a corpse after periods of time. Even the predator showed such coloration in his skin. It also seems that infectoids don't have to see with their eyes, as they always have their heads limp when they fight in AVP arcade.