I recently traveled through Addis Ababa, but I only saw the airport while waiting for another flight. FWIW, Ethiopian Air seemed like a nice enough airline (I've still got the golden sleep socks and eye covers they issued on the plane). On my previous visit (in 1998) war broke out between Ethiopia and Eritrea just as we landed at Addis Ababa and so flights out were very hard to get.
Obviously, the place is a lesser developed part of the world and so standards will be different from those of more developed spots. This should go without saying (and you're probably looking forward to the adventure), but you should have heard the newlywed couple who boarded our plane after their safari honeymoon in Tanzania. They apparently expected things would be just like Boston, but with giraffes. Surprise!