I got an Ethiopian visa in Khartoum without too many problems just a few months back. The embassy has recently moved from its stated location in LP to a few blocks further East in a large open compound.
I arrived at 9am the first day and was told visas were 'finished' for the day. It turns out they have a quota: only 30 are issued each day. First thirty people to arrive get a visa, issued same afternoon if you're lucky, next day if not. Anyone who arrives after thirty application forms have been handed out, is out of luck.
In practice this means you need to get there by 8am to be sure of getting a form. This guy come out with thirty forms and hands them out outside the gate, often before the place opens. Once you've got a form, you're in. At busy periods, before holidays and such, you need to be there by 7.30 and queue.
Cost was USD 30 and service inside was pretty quick and efficient once you get in. Take photos with you though as there's no facility for taking them in the embassy and they won't hold your slot while you go and find them.