I think Cunard made a mistake by not doing something about the 5 deck cabins (and some/all of 4 deck) a long time ago. Most of the cabins on 3, 2 and 1 deck are lovely. Our midships cabin on 3-deck was absolutely lovely - all the original features were intact and in great condition. It was spacious, with I think 12+ large drawers, and tons of walk-in wardrobe space, it was far more luxurious than most of the plastic/mdf staterooms on QV.
We met a couple on our August cruise who had enjoyed their trip, but were very definitely clear that her day was past, and i don't think they'd have gone on her again. And yet, my Mum and I were thinking she looked as good as new, and we were champing at the bit to book another trip! They were in 5 deck.. I think many people who stayed on 5-deck, didn't appreciate how many of the cabins "above" were nice, without costing a fortune... the middly-grades ones. I was also surprised to find that our 3 deck cabin was absolutely identical to 'singlemalt' ali's cabin towards the back of 1-deck, despite it being a number of sub-grades higher than ours.
Most of the signs of neglect and tiredeness i saw were easily fixable, and were mostly outside.