I remember the old days before Bole International airport was completely renovated. You had cardboard signs and flimsy plywood desks greeting you upon arrival. Now, you enter a sleek, modern airport complete with decent shops and friendly, fairly customer oriented people. Upon my last visit, custom clearance continued to be slow but you will get through so don't worry. Taxis are still a hassle. If you want a worry free trip into town and no one is picking you up, take the yellow government taxi's parked at the terminal to avoid haggling and over-pricing. Also, the toilets seem never to be stocked with loo-role so it's a good idea to bring your own along with some travel soap. All in all, Bole should be a pleasant experience for most travelers.

When entering from the street, there is an X-ray check for all luggage and metal detector frame for passengers. As both cabin and heavy luggage goes to the same x-ray, be prepared for not careful handling.
Before visiting the passport officer, you need to fill the departure card. Passport control is a very slow process. Bank/exchange is 2 floors down and they usually don't have Euros.

I visited Ethiopia in March 2006. I received my 30 day visa at the airport, it was only $20.00 USD. It was quick and simple with no problem at all. The people in Addis Ababa are very friendly.