Boy, I hate to be odd man out here but somebody has to play devils' advocate!!
I would pay to have my flight changed to an early morning or even better, a late afternoon/early evening the day before. But, that is me. At the very least, do an early morning flight. I would hate for you to miss the cruise. If it is not through RCL, then you could do that. We just got back from our December cruise and we had several delays on our flight down. Nothing that would have made you miss the flight but you would start out your cruise feeling rushed.
Lets look at the times. You must be onboard 30 minutes early. That means 4:30 at the latest. By the time you get your luggage to a porter, give a tip, pay the cab and get inside and on the ship, you are looking at a minimum of 30 minutes. The time is now 4pm. Now, take into account the taxi ride from the airport and it is now 3:30pm. Go back even more to getting off the plane and rounding up your luggage. If you get it in 30 minutes and are outside waiting on a taxi, you will be very lucky. Now, you are at 3pm. You said you are scheduled to land at 12:41. In airline talk, that means that it will be after 1pm, guraranteed!! So, you now only have a 2 hour window to play with. On our flight to Miami, AFTER we were on the plane, we sat on the runway for nearly an hour because of a backlog of aircraft taking off. We were number 21 in line for departure!!! Talk about frustrating! If anything like that happens to you, now you only have an hour!
If everything goes without a hitch, you will be fine as the others have said. But, I gave you the devil's advocate approach because my luck usually runs that way!! My vote is to change the flight. My vote would be for a 10 am or earlier. Preferably 8 am. Remember, you can be on the ship before noon if all goes well on most cruises. Good luck either way.