Hi. Haven't been on the QE2 yet, but planning a trip, so have been studying the deck plans and talking to people at Cunard lately. The guys told me that the Q2 cabins (the pink ones) on the top deck, have no problems whatsoever. (Considering the prices, I should hope NOT!)
On the second deck, the "obstructions" often mentioned, are only when you stand on your veranda and look DOWN -at the lifeboat. You have NO obstructions if you are looking straight OUT., sitting or standing. Of course you have to (at your peril) lean way out and look to your right or left, to see forward and aft, views, as all verandas have walls between them for privacy.
Now, as to Q3, the yellow cabins (on the deck plans), on the third deck down, WATCH OUT! There are only 8 and they seem very desirable, BUT they are right on the Promenade, and have very large windows. IF you are inside with ANY light on, people out on the deck can SEE right into your room! The windows are treated so if there is ordinary daylight and you have NO lights on, people outside CANNOT see in but on a cloudy day or when dusk comes, or if you are trying to read something, you may very well turn on a light and not think about the fact that you are now "on stage". (We crossed off that deck for that very reason. I refuse to worry about visual privacy and I refuse to live like a MOLE!)
I was also warned that nearly EVERY cabin on the QE2 is different from every other, so STUDY the room sizes, no matter what the chart looks like. Remember, as in most of life, caveat emptor. (And for those of you unlucky enough not to have had to take 5 years of Latin, that means "buyer beware." )