You might be pleasantly surprised. I always have a bottle on each cruise and, so far, every one has been excellent - complex notes, sweet (but not the cloying sugariness of cheap Sauternes, say) but with a distinct, almost citrus, tang. I'd also add that the sommeliers have always ensured the open bottle is properly stored. I drink very little alcohol so a 375cl bottle lasts 5 nights.
Sadly, dessert wines, at least here in the UK, have a tendency to be syrupy and therefore often an ignored treasure. A good Eiswein or Tokaji will hold its own against d'Yquem - as you alluded, however, it's finding a good one that's difficult.
(Incidentally, in my opinion, the Tokaji and Chateau d'Yquem on the SS connoisseur's list are a bargain. Well under retail.)