I have heard from a couple of people in Ethiopia that khat is taking over. Its also running peoples lives as they live from "hit" to hit, making them lazy and they pounce on the khat dealers as they come into town with fresh stuff.
So from a social aspect, khat sounds bad. From a coffee perspective its even worse as small holder farmers are pulling up great cofee trees and planting the faster growing khat.
Im sure you will have some great coffee with locals and Im sure I speak for all in saying bring back plenty of photos and stories".
Have a great trip!