Richard,
I'm afraid I've only traveled M class, but aside from the dining rooms most things are the same. The majority of the solo travelers are older females (I'm in my 30s, so I do stand out a bit).
They always have a get together for solo travellers, and make a point of seating you together at dinner. I'm rather outgoing, so I usually just ask to join other solos at tea, etc.
The bartenders are great at making solos comfy; one of them remembered me from the previous year (I'm not that much of a lush!), and the waitstaff will look after you at the meals without assigned tables.
I took a transatlantic crossing two years ago, and really enjoyed it. After the first day at sea, cell phones no longer work (yeah!) and you can go hours or even days without seeing another ship. There are a lot of activities, but you can also just stop and relax. The Atlantic can be chilly in the shoulder season, so they'll bring you a blanket and you can curl up in a deck chair with a good book from the library and a cup of tea.
I'm sad to see that the QE2 will no longer be doing the crossings. QM2 is too big for my taste, and the absence of single cabins is disappointing.
I hope you enjoy the QE2. I spent a week in the Med on Costa this spring , and really missed the QE2.
-Julie