I have to add Luanda was my first real Africa experience besides from Johannesburg. The biggest problem at this airport is the old lacking infrastructure and not enough space.
At the same time SAA/BA/TAP arrived making the arrival hall (one room) quite tight, especially around the one (1!) guy checking for yellow fever. After this, immigration was efficient and OK, same as luggage handling which was no problem at all. Taxi service is poor, so better get a ride with somebody you know. When leaving the country there is only one very small check in hall, it looks quite disorganised, but worked well and without problems. Checking by customs for local currency was ok and professionally handled. Infrastructure (toilets, cafes and what is called duty free) is medium to poor, however it works. Angola is planning to build another airport outside Luanda to adjust growing passenger numbers.