We took the train from Dar (Tanzania) to Kapiri Mposi (Zambia). It was supposed to be a 41 hour trip, but actually arrived 47 hours and 45 minutes late! 4 days is a long time to be on a train! I am in the process of writing up a detailed account, but in the mean time here is a link to the only high point of sitting in a train station all day:

Photos of Zambian kids in the Kasama and Mpika train stations.