This new mob is supposed to be released in the next update(1.8), here is just a run down to give you a glance at all the chaos this mob will cause.
Enderman have the ability to pick up and move blocks around. They are generally a peaceful mob, but if you look at them, by placing your crosshair directly over them, they freeze, stare back at you, and become hostile. They stay frozen as long as you keep looking at them. As soon as you look away, they will quickly run towards you; if they are a long distance away, they will teleport several times until close enough to reach you. They will only teleport to somewhere you can see. Endermen can teleport about once per second. There is one weakness of the Endermen, they take damage from coming in contact with water.
Even though they may not seem as deadly as the Creepr, I can see the Enderman becoming one of the scariest mobs of Minecraft.