Holy crap! I'm playing my Prince game that I started in the 2nd era and the barbarians are simply amazing. I've seen so many hunters, horseman, and axeman that it wouldn't matter if there were no AI civs because I'd still have just 5 cities after 200 turns! The horseman are particularly nasty with 3 moves and they know enough to move 2 and then pillage. 
The map is always filled out when you start a normal game so you never see barbs like Hunters or Horseman, but since the barbs have the tech they obviously know how to use the units....

The map is always filled out when you start a normal game so you never see barbs like Hunters or Horseman, but since the barbs have the tech they obviously know how to use the units....