We just returned from a six week trip to Ethiopia and despite being there during the state of emergency had almost no problems or issues. The only place we couldn't go was the Laga Oda rock art site near Dire Dawa. At the time none of the area guides would take us citing unfriendly locals.
Here is a breakdown of our trip; we used a combination of internal flights, public transport, and guided tours (as stated):
Lalibela, Axum, Yeha, Mekele.
Danakil- four day ETT tour.
Hired car and driver from Simien Image (see below) for a six day trip to the Blue Nile Gorge, Debre Libanos, Guassa Community Conservation Area, and Awash National Park.
Dire Dawa and Harar.
Eight day Omo tour with Simien Image.
Shashemene.
Hired car and driver from Bale Mountains Eco Tours/Bale Trails (www.baletrails.com/index.html) for four day trip from Dinsho through the Bale Mountains and Harenna Forest, and on to Dolo Mena for the Prince Ruspoli's turaco (which we saw). Ayuba, our Bale guide, is highly recommended. He knows the area intimately, is well organized, and has an excellent conservation ethic.
We were lucky early on to get in touch with Alex of Simien Image Tour and Travel (www.simienimage.com). After a day trip 'test run,' we ended up with him and his extensive contacts all over the country for the guided parts of our trip. Alex is honest, easy to get along with, knowledgeable, obviously loves Ethiopia, and is a really nice guy. In fact, we consistantly got positive comments about Alex even from competitors. Without Alex our visit would have been much less enjoyable.
Beyond these comments I highly recommend the latest edition of the Bradt guide for specifics.
If it's within your comfort zone, now is a very good time to visit Ethiopia. From a purely selfish point of view the lack of tourists makes travel much easier. We had no trouble finding transport, rooms, and guides, and popular places like Lalibela were almost empty of foreign travelers. It's heartbreaking, though, to see the impact on those Ethiopians trying to survive by tourism and who want to share their wonderful country with visitors.