Like you, I read lots of the reviews of the QM2 before we sailed, and had fairly mixed feelings about the trip as a result. Having now sailed on her, overall, I'd say most of the plus and minus points other reviewers had mentioned are quite true. We've sailed with RCI and Celebrity before, and Cunard slots into the middle Cunard was way better than RCI, but not as good as Celebrity. However, being on an ocean liner (as opposed to a cruise ship) was an amazing experience, and I'd definitely go on her again.
Embarking at Southampton took a while, as the gangway to the ship wasn't working, so a fair bit of waiting around until it was repaired. Once it was, the rest of the process was quite quick. Cabins were nice, fairly standard in size and layout, with plenty of storage space for a seven day cruise. Two of us had balconies with metal fronts, and two of us had glass-fronted balconies. On the whole, the metal fronts weren't as nice, as once you sat down you couldn't see the sea over the top of the balcony, but other than that it was fine. I think in future I'd shell out the extra and go for a glass front instead, though. Comes down to do you want to gaze at a metal wall, or at the sea.
The ship itself looked worn out in places, especially with the lumpy carpets in the high-traffic areas, but the overall impression was still that it was a beautiful ship. We were in the Britannia, and the food was nice but nothing amazing. Nouvelle cuisine style portions meant you never left the restaurant feeling particularly full! The Kings Court buffet area really is like a cafeteria on a cross-channel ferry, and we eat there one evening. The food was noticeably better than the Britannia, but then you were paying extra. The vegetarian option on the menu meant that they fetched you something from either the Britannia or the Grill restaurants, which rather defeated the point of eating there in the first place. But if you wanted meat, the meals were excellent. The area isn't shut off in the evening, so lots of people are walking past you as you eat, so it still had a cafeteria feel about the experience. Generally, the food side of this trip was the least appealing aspect of the experience, but where ever you eat, you certainly won't go hungry.
Entertainment was fine the talks were interesting and well delivered. The one hour Hamlet was funny if you knew the play, and completely mystifying if you didn't. It wasn't supposed to be either, I suspect. Good turnout for it, but then on the way back to the UK the production of the Canterbury Tales had a much smaller turn out. People obviously had learnt their lesson, which was a shame as this one was really quite good. They do a 50 minute version of the Importance of Being Ernest as well, apparently. I can see the snob appeal of putting on these shows, but if you like Theatre you'd probably only want to see them in the same way people can't help staring at a car crash and wondering what happened. The dancing in the Queens Room was impressive many of the passengers clearly know what they are doing, and it was a pleasure to sit back and watch, especially with live music. Afternoon tea in the Queens Room was very crowded, and nothing particularly special. Nice enough thing to do if there's nothing else you'd want to do, but the same food is served in the Kings Court buffet, but without the long wait.
The ports of call were great. Two other cruise ships were docked in Stavanger, so our plans to get a local trip to Pulpit rock were scuppered as all the places were full. Not much else to see, although the old part of Stavanger is really very pretty. We headed back early to ship and went to the Spa, which was wonderful. I'd cruise on the Queen Mary 2 for the Spa alone lots of different water treatments to experience, and a lovely relaxation area overlooking one of the decks.
Alesund and Geiranger were pretty; we took tours with Cunard for these. They were well-organised, and we enjoyed them, even if they were a bit pricey. In Bergen we made our own way to the funicular, via the courtesy shuttle from the ship to the city centre. Nice place to wander around, and we were lucky with the weather the whole trip which was a big bonus. The ship was stuck for a while in Bergen, as one of the pods wouldn't start, but leaving Bergen and passing under the bridge was a great experience. Lots of waving to the people on the bridge, and quite a party atmosphere.
In seven days, we really didn't feel we'd gotten the hang of the ship, and it felt like there was still a lot to explore. The service was a bit hit and miss, and it did feel rather impersonal at times. Certainly if you are looking for things to complain about, you'll find things quite easily, but we had paid for this as a last minute deal, so there was a sense of for what we'd paid, this was fine. Celebrity crew seemed to work far harder to make your trip as pleasant as possible, and this was definitely not the case on the QM2, but it's still an amazing ship, and Norway is a beautiful place to visit. So whilst you may not want to go on her again, don't worry about any of the negatives you read - you'll still have a great trip.