My family and I (Brit, Chinese, Chinese on Brit passport) are all getting visas on arrival next week, albeit at the Laos airport.

Luang Prabang, although I liked Vientienne just as much. If you see some of their Laos sausages on the menu, I suggest you get one. They were very nice.

Have a good time.

I've read that visa on arrival requires payment in US $.
Can anyone confirm that?

Fly in to Vientiane. You can get a visa there, every country and currency fave a different rate. Buses are brutal

Note carbon footprint problem. Lots of foreigners bicycle - Autumn and Winter are best (hot now, then rains). I have found views from buses to be interesting.