Couple of additional info points: used VoA at DAD - one in our group had ordered online visa in US passport, while other two had non-US passports and VoA was the only option for them.

At DAD - and I can tell at SGN snd HAN as well - it is a lottery how much VoA processing will take time. At DAD this time it was shortest - no one was waiting at the counter in line when we arrived and visas were ready in passports 5 min later. Situation did change 10 min later after arrival of three planes. There was at least 20 min wait for pax who had to stand in line. Yet it was way better than the very first experience with VoA at SGN 4 years ago when it took an hour to get visas in passports.

And then - there is separate wait in line for immigration control- it was 30 min wait and while there was separate booth for APEC cards, it was useless because they lined up all ordinary pax there.