Of the three kobolds in the Essentials DM’s book, two (kobold tunneler, a level 1 minion and kobold quickblade, a level 1 skirmisher) are new. The Kobold Slinger is updated from the MM1.
The Kobold Slinger’s attacks have been made more accurate, and damage has been slightly fiddled with, but the big change is that Special Shot is now a random effect. Instead of the type being chosen by the DM, Special Shot now requires a d6 roll: on a 1-2 it’s a Stinkpot, 3-4 Firepot, 5-6 Gluepot.
Someone at Wizards is going back through old rules and adding random die rolls!
Do you think his name is Mike Mearls? I do! But maybe I’m wrong!