I have no experience on around the world but I use to have a Tandem and I was in Vietnam with a Tandem and a B.O.B you can see some pictures
http://www.der-radladen-mannheim.de/html/fotos_links.html
After I go back I decide to sell it,I prefer better on a single bike,is much easy to fly and to catch a bus on the way,also when you are on a Tandem people are freeking out when they see you,we been in Vietnam for 6 weeks and we have very small moments for our self
Saludos