Sorry for the

, OP...
I never even thought about going a day early. Good idea. What time does the ship leave and what time do you get back? Do most of you use Disney transportation (which I am surprised is not included) or rent a car? Who do you rent from? And do they pick you back up after the cruise?
Also what time is a good time to schedule a flight on the return day? ....
Arriving the day before is a no brainer for us. Especially these days as there are fewer flights, which means less flexibility to get you there in the event you get detained for any reason. Also, as I've been flying in the past year, it seems there are more and more delays than there used to be. That's just TOO much stress for us. Furthermore, if your luggage gets lost (which happened to me recently on a direct flight), if you're arriving on Friday, that gives it more time to get it to you before you set sail.
The ship leaves port at 5:00ish, but if I remember correctly, I understand according to Homeland Security everyone HAS to be on board by 4:00, which is also about the time for the muster drill. IMO, you realy should be on-board by 3:00.
DCL buses vs. renting vehicles or a limo/town car can be a decision based on finance or preference. Depending on family size, it may be less money to rent than take the bus.
If you're flying in the day before and want to take the bus, obviously you will need to stay at an airport hotel to pick up the DCL bus on embarkation day. Many perfer to get in the day before and stay at a hotel in Cape Canaveral or Cocoa Beach, which puts you back to renting or getting a limo/town car. Rental car companies do have shuttles to/from the port. Check out
http://www.disboards.com/showthread.php?t=1520273"] loving Shirley's awesome thread, which will answer a lot of your questions around rental transportation as well.
As for debarkation day, DCL recommends you do not book a flight before 12:30 pm. It's unpredictable what time the ship will get the clear from Customs to start allowing passengers off, although it could be as early as 7:00ish. With that said, you'll read that many people here have flights at 10:30. Again, I'm not a risk taker like that (What if we don't get clearance to get off early in the morning? What if transportation method back to the airport has breakdown issues or traffic delays? etc.), but you may be willing to take that risk in order to get back home to the farm.
Now...back to the OP's thread question!