Freighters, Mail Ships, etc.

[Fisch]

Has anyone ever sailed on a freight ship or mail ship as an alternative to the big ships? I'm a bit curious as the prices are very affordable. I do understand you do not get nearly what you would get on a big ship but seems like a more adventurous way to cruise. The Norwegian mail ships sounds interesting. I would pay little for the cruise and spend all of my money on excursions.