I was in Amsterdam this past April, and saw the Anne Frank house. If you're interested in history at all, you should see it. A few words of advice: buy your ticket online ahead of time. Go either early in the day or towards closing time, unless you really like standing in line for a very long time. Be prepared for crowds, regardless of when you go. The number of people going through tainted the experience for me a bit, since it's difficult to get a sense of the place with 40 people shuffling through each room with you. Still, I'm glad I did it.
Amsterdam is a lovely city; I've been there twice and enjoy it very much. I haven't signed up for this cruise, but I am thinking about it, mostly because it goes through the Alsace region, which is where my great-great-grandparents came from.