We have done two Transatlantic cruises on QM2. Deck 8 balcony stateroom, Brittania Dining room. The only things we had to pay extra for were the same as on most ships, the Ranch Spa, hairdressing, beauty treatments. casino, photographs, excursions etc. (The Ranch spa shampoo is provided free of charge in the staterooms, a great product). The Planetarium is free, and well worth a visit, but you have to book ahead, as places are limited.
The food is first class, so is the entertainment, and if you are ballroom dancers, there is a full sized dance floor,(the Queens Room) with dance band, for your pleasure every evening. The Queens room also hosts afternoon tea's, DELICIOUS.
The "segregation" Mr Gresham refers to is simply the fact that Grill passengers (Queens Grill and Princess Grill) enjoy bigger and better cabins, separate dining rooms, their own sun deck and lounge, and use of concierge services, all of which are included in the higher price that Grill passengers pay than Britannia passengers.In the use of all other facilities, Grill and Britannia passengers are treated alike and the things you pay extra for are the same as any other cruise line.