I did the QM2 Westbound Transatlantic and I loved it. It isn't at typical cruise, it is an ocean liner, and you really experience it as an ocean liner. It takes 7 days to cross. The ship can do it in five days, if necessary, but they keep it at a steady pace to make it a seven day journey. There are several different classes: Regular, Club, and Grills. We sailed in the regular class, which I personally would prefer because I like dining in the big dining room. The Club class has its own dining room, and each of the Grills have their dining rooms as well. But there is nothing like the big room, at least for me.
Three of the seven days are formal, which means tuxedos and evening gowns for dinner. That was probably my highlight, drinking champagne in the champagne bar surrounded by everyone in formal attire, it was spectacular.
The Club rooms are basically the same as the Regular rooms, but the Grills rooms are much bigger. With the top level, you have your own butler.
QM2 is a fantastic experience.
And once you catch the QM2 bug, you need to watch the lecture from the architect.
It is a bit long, but it is really enjoyable and helps understand the uniqueness of the ship.