Actually there is little class structure on the QM2. It is not “in your face” as it is on Celebrity. You will not board on red carpet or be escorted to special seats in the Theater. There is one lounge for Grill passengers with a concierge, tea and pastries. It’s in the middle of the ship on a passenger deck, no windows and nothing fancy. There is also a bar for Grill passengers with a pianist. It’s not restricted as we have had many friends join us for cocktails. The Grill Restaurants are the only really restricted areas. No outside area to speak of on the QM2. We really enjoy the themed crossings and last December we were on a Literature cruise with 27 best selling authors (UK) and the Editor of the New York Times book review and the London Times book review. The crossings typically have some theme or special artists. We missed James Taylor and Carly Simons but you can see some of their performances on YouTube.
It is something you need to do at least once, consider it.