I think it's preferable to arrive a day prior to cruising, however for short getaway cruises, I have arrived same-day many times. My biggest concern is the possibility of a weather-related airport closure, but (knock on wood), that has yet to be an issue.

As I said though, if it's possible to leave a day early, it does make things less stressful. I have an upcoming short cruise that we did opt to fly in a day early for, primarily because the airfare was significantly lower and the flight times better. Of course you have to factor in what you pay for a hotel room, but I'm always willing to pay a bit more if it means getting the flight times I want.