The room was great, lots of space and great service. People complaining about having a hard time getting around the ship, I do not agree. It is a large vessel but manageable.
The highs -- staff, the ship, the people -- not all old (I am 37 and met many my age), the food (except the food court -- I do not do buffets), the spa we used 5 times -- great, Todd English was the best (I had two meals) and service most of the time. No problems with reservation at the spa or Todd English, but do them early.
The lows -- port of call visits too short, tendering was an adventure for my wife, not for me. Poolside band was not out long enough and drinks were hard to get while in the whirlpool (tough life). Also, they seemed to nickel and dime for soft drinks.
I would use the QM2 again. We had rain and a cold/kind of rough first night/day and it was still worth the money.