I honestly can't think of anything that would be a 'deal breaker'... some things happening last minute would be a disappointment, other things might make me look for a different ship, itinerary or sail date...
Now I have my PREFERENCES- balcony, 7 day or more, newer ship, cruise date with fewer kids, cheaper cost, new ports... but hey, I'd take a 3 day Bahamas itinerary in an interior on the oldest ship, if it meant I could cruise!
Now He Who Will Sulk (as opposed to She Who Must Be Obeyed) often overrides many of my options! But since it means I'm getting a cruise, I don't usually complain!