I am afraid that I just don't understand the appeal. Opportunities for genealogical instruction are great, but I'm not convinced that the cruises are for everyone.
One draw of the land-based conferences is that I don't need an entire week or more of time off work to attend. In fact, I can even attend half of the conference if I so desire..and I can leave whenever I need to. This gives me great flexibility. I have too many obligations at home to be gone for over one week.
The exhibit hall is another huge draw for me as well. And personally, I would love to spend either a week in Richmond or in Ft. Wayne. There are excellent research facilities in both venues and Richmond offers a close proximity to a wonderful variety of historical sites for the genealogist who is not from the area.
And if I ever get to go on a cruise, I don't think I want to be attending lectures, classes, etc. every day while doing it. A vacation is supposed to be a time to "get away," not a time to "drag it with me." And I know me...the chance I go on a cruise is close to zero. If I get the time and the money, I'm visiting ancestral homelands in Europe--I'll leave the cruises to someone else.
Of course my opinion is biased. This is written by someone whose never been inside a casino or made the thirty mile trip to visit one of the Mississippi riverboat casinos either (nor have I ever bought a lottery ticket...)