Since this board has been very useful, I wanted to contribute my experience on the Queen Mary 2, in April 2006.
Embarkation: I flew from NY to Heathrow; there were several easily located Cunard reps gathering people for the transfer to Southampton. We killed time for 90 minutes, then hopped on a bus to a local airport hotel for Cunard's courtesy lounge (tea/coffee & cookies) to kill more time so that we wouldn't arrive at the pier too early to board. Luckily, we only had to spend 20-30 minutes there but it was nicer than remaining at the airport. Embarkation at Southampton was awful - the worst I've ever seen. The problem was that this particular sailing included 400 passengers who had disembarked from the QE2 that morning (the end of the world cruise) and had transferred to the QM2 for the trip back to NY. With 400 passengers at one time, the check-in process was extremely slow and then there was another line to go through security and then a holding lounge before being allowed to board the ship. Luckily, I'm a platinum member so had priority check-in which bypassed one line and allowed me to scoot into the security line. But most people were very cranky. Once on-board, I went to my cabin & got organized.
Cabin: I booked an inside on Deck 6 which was fine. Nice decor (light woods, gold/gilt duvet) and plenty of storage for one person. Good lighting, mini-fridge, TV, & all the normal conveniences. (Good heat/A/C controls which were quiet and accurate). Bathroom was small (shower only) but that's what I expect. This cabin (#6213) was near stairway C which was fairly mid-ships which is handy for traipsing all over (up/down and end to end). Once in a while, I'd come down Stairway A, and boy, it seemed miles away from my cabin! Steward service was fine - unobtrusive.