You'll have a wonderful time. We were on the 2007 Barcelona to Miami transit and had a great time. We also spent 2 nights in the AC Diplomatic, one the Oceania-arranged hotels.
Here's some observations. The hotel was clean and well located in Barcelona. It was really set up for business travelers and not tourists, but that really wasn't a problem. Having experienced the Oceania-arranged hotel stay, the next time I would probably arrange my own hotel and transportation and save some money.
The one thing we didn't plan on was the weather. This was our fifth transatlantic cruise and the weather was considerably cooler than I expected. I was expecting temperatures in the low 70s and the temperatures averaged in the upper 50s. Also, the ocean was very rough. The roughness of the ocean is a crap shoot, the temperatures are another matter -- poor planning on my part. The ship, the staff, the food, the service, ... could not have been better.