We just got our final papers to leave on Jan. 8 to caribbean. There was nothing to pre-register our credit card and no way to book excursions. On Princess, we did it online, Cunard doesn't offer that. When do we register, on board? Aren't the lines long? What is the scoop?

Check the Cunard website FAQs, they address the issue of registering your credit card before the voyage.

There is a FAQ but there is no answer posted re: paying for things on board

I believe you simply quote your card number, and then settle your bill at the end ... doesn't the FAQ tell you that? Or did I misread? Please call Cunard and ask them - 800-728-6273 - opne 6 to 6 PST. By the way, one FAQ I just looked at says you will register your credit card at check-in, and then settle your account at the end. Or am I missing your point?

We just returned from the 11/26 to 12/6 cruise to the Caribbean on QM2. Cunard registers credit cards at check-in.
We had to wait until we were on board to book shore excursions. But it was possible to book them in our cabin, via the interactive television, i.e. no lines. (We booked the first afternoon on board, and were able to confirm every excursion we were interested in.)
If you are interested in any of the alternative dining venues for dinner, I suggest you book them the first day as well. We enjoyed Lotus (Asian cuisine) and Todd English. Cunard had a restaurant manager taking reservations on the pier, prior to embarkation. You can also book the restaurants via your cabin phone.

Thank you jcnyc. how was the cruise, did you engoy it?? It is a little more formal than other ships, i.e, can I walk around in my red sox t shirt?? Thanks for any info you can give us!!!

We had a good time. We stopped at St. Maarten and St. Thomas (as you will), but not San Juan (went further south).

It's a big ship. It doesn't seem very crowded except at buffet time. The ride was very smooth - almost no pitch or roll.

We enjoyed the promenade deck, the planetarium (free tickets available at 9am each day at the Connexions desk - first-come, first-served), and the shows (young, hard-workng, and versatile cast of singers and dancers).

At St. Maarten, took a tour which included sunbathing time at Orient (French-side) beach - wish we had more time at Marigot.

At St. Thomas, took a kayaking and snorkeling trip - similar to trips offered in the Florida keys.

Dinner in the Britannia restaurant was fine (food and service). Breakfast in the Britannia was very slow (kitchen problems, I think), so we ended up eating most breakfasts at the Deck 7 buffet. Lunch was a little better, but we took most lunches in the buffet or the Golden Lion pub.

During the day, many people dressed in T shirts or polo shirts for recreation (but not Red Sox - please, our cruise was out of New York).

Evening wear was dressier than I expected. Many men wore suit jackets or blazers on "casual nights", even though the dress code didn't require it. About half (maybe more) of the men had tuxedoes on formal nights.

Interesting report. Did you receive a map of the ship beforehand ... if not, where do you get it?

No, we didn't get a map to the QM2 in advance, though there is a pretty complete interactive guide on the Cunard web site.
On the ship, Cunard stocks each cabin with a pocket-sized map. Each stair landing has an overall map to the ship and a detailed map of that deck.
This is the biggest ship I've been on. Even though we could find our way around by day two, there were still little corridors and nooks to discover, up to the last day.