Our previous two cruises were both with Celebrity so it is in this context that I comment on our QM2 experience. First the good points:
Our cabin even though it was a 'port-hole' class on Deck 6 near the bow was excellent and I couldn't fault it. Our steward was quite shy and retiring; he did the job but we saw little of him. The beautiful Art Deco theatre called Illuminations was excellent and had a superb Planetarium feature. The gym, once we found it, was very good. I say 'once we found it' as the various direction signs and listings didn't mention that it existed. The Ballroom and the teas served there in the afternoon was excellent and the evening dancing and band was very good.The shows in the main Royal Court Theatre were generally good; in particular the acrobatic duo. The session speakers were mostly good and the Jackie Stewart talks were excellent. Service from staff was generally efficient. The main restaurant, The Britannia, was very attractive with excellent decor.
Now, the downside:
Our cabin was 6013 on Deck 6 near the bow. It was perfectly OK in all respects for this class of cabin. It is near the gym, library and theatres but a bit of a walk to the restaurants