We’ve just had news of two companies offering luxury coach services (or what passes for luxury in Ethiopia) along several major routers. In both cases the coach are meant to provide a compromise between expensive flights and rough local buses, and they are aimed at middle class Ethiopian as much as tourists, so not madly expensive. Both have useful websites, if you want to explore further.
Sky Bus started up in Dec 2008 and offers services from Addis Ababa to six major cities, namely Bahir Dar, Gonder, Jimma, Awassa, Harer and Dire Dawa.
Selam Bus runs services to Bahir Dar, Gonder, Jimma, Harer, Dire Dawa, Jijiga, Dessie and Mekele, and even has an online reservation system.
Any feedback from travellers who use these services will be greatly appreciated!