I put on image ads the day it was announced. I didnt get to see any until yesterday (which doesnt mean that it wasn't on earlier). The overall result for the last 4 days was really bad. EPC halved! I dont know if this had anything to do with it but I switched off image ads and my EPC is back to normal after 14 hrs!
Coincidence? Probably but I think I'll wait a while until I see them around a bit more, get feedback from other publishers and probably will put them on for specific channels next time so that I will know for sure.