I've done Heathrow to Rio and back twice, Heathrow to Houston and back five times all on BA 777-200, Hong Kong - Singapore on SIA 777-200, Auckland to Rarotonga and back once on Air New Zealand 777-200, Singapore to Melbourne once on SIA 777-300 and Auckland to Los Angeles once on Air New Zealand 777-300. I have done Frankfurt to Houston and back once on Lufthansa A380. All flights down the back.
I've done a good number of A330 long hauls - I hope the A350 is an improvement, though Aer Lingus aren't exactly up there when it comes to their cabins.
Apart from the SIA rides and the Air New Zealand 300 rides where the cabin service was the better part of the experience and slightly colours the overall feeling, the A380 is quieter, feels roomier, is more comfortable in turbulence and seems altogether more a passenger's aeroplane than any large twin.
To those willing the early demise of the A380, go back forty years and see how the 747 was doing in a market where nationalised or flag waving airlines ordered the biggest aircraft they could buy out of pride with very few, if any, slot restricted airports. Take off the Boeing coloured spectacles and, while the A380 may not in the long term equal the 747 for numbers built, realise that engineering, ramp space, slot restrictions and passenger comfort, even down the back, all militate for double deck VLAs.