After a few games using the Peacekeeper, it feels like a solid weapon. The description is perfect: an SMG/AR hybrid. It doesnt feel as OP as the Scorpion or the MSMC - but the few games I played with it, I did very well. Actually,first time playing Grind I got my swarm playing domination.
In relation to the Camo for the PK - You need to complete ALL the challenges to obtain diamond camo (just like any other gun)!