Mrs. Info and I took two of our grandchildren (8 and 5, both boys) on the QM2 in June, 2006. YMMV, but our impressions were uniform, and independently arrived at.
We've been on a boatload (sorry) of cruises in the Caribbean ,the Mediterranean, and in South America. None in Asia. Yet. I've been on the QE2at the Captain's Table on one Crossing, although I was alone on that trip.
Our impressions were that the ship was not nearly so formal nor the passengers well-dressed as we expected. The summer date of our sailing may have affected that, but it's hard to tell. Not that there were not well-dressed people aboard, but it was rather quite a bit less than we expected.
The library is extremely good. One could find enough to read there to read all the way across the Atlantic and barely dent the choices available. The shipboard entertainment is, in our opinion, mostly a cut above the level we found on other ships. The quality was not uniformly high, but the breadth of high-quality lectures and entertainers was pretty clearly better than almost any other ship that we had ever been on.
The food we thought was "OK." Frankly, it didn't suit us very well, but, again, YMMV. The young boys thought it was "great." But they are young and eat anything. I would have called it "fairly high quality mass cooking, but not that high." There are a few restaurants on board that require supplemental charges and I did not include those in my general evaluation in the prior sentence.
It's a big ship. That may be good or bad. To the OP, I'd say that the season makes a difference (summer was good weather generally) because you can get out on deck more consistently in good weather.
For any parent or grandparent reading this, the QM2 does an absolutely fabulous job taking care of children. They have a number of college-age men and women who do a delightful job of entertaining the younger set during morning and afternoon sessions at dedicated facilities in the stern area.
The "art" sales held on board are abominable. Totally commercial and directed at those who assume what is being sold has some taste associated with it. They would assume wrong.
The costs of Cunard-sponsored travel to London and elsewhere from Southampton can easily (very easily) be beaten. It's incredibly easy to simply get off the ship there (if you can carry all your luggage off in one trip) get a taxi and go to the rail station or coach station. And, by doing it yourself, you can get off at the very first opportunity that anyone has. The amount you pay for the "convenience" of having Cunard do the arranging for you is very substantial compared to doing it yourself.
As I said, it's a big ship. If you need to be diverted and entertained, there is plenty to do. But maybe not enough. We found it relaxing to take a nap, have choices at various times throughout the day and evening for entertainment but not be forced to do anything.
The internet connections are so horrendously expensive that I shudder at the memory. If you were thinking you'd entertain yourself via the internet on board, you'd be better off to just sit at home and continuously light dollar bills and watch them burn.
I appreciate that this is not a full review of the cruise, but the items mentioned above are the standout memories some six months later.
It is a very relaxing way to spend six days getting to Europe. If you have the time, a one-way Crossing is fun. I don't think I'd want to do it very often, though. The ratio of pleasure/fun to time is less than we like. But, again, YMMV.