A couple of thoughts re. the 787 and the fuel savings; whilst the airframe appears heavier, how much of that equates to fit out? All that IFE equipment is pretty hefty and wasn't present in a 70's airframe. The majority of the 787's fuel savings come from drag reduction and the lack of stealing bleed air for pressurisation.
The A380, it should be remembered that it carries a load of freight payload per revenue flight, which isn't costed into the passenger v kg figure.
Anecdotally I was told that when Air NZ stuck winglets on their 763's (soon to be replaced with 789's) they also sent them away to remove excess water from the insulation. The figure quoted was there was approximately 3000kg of water accumulated in each aircraft - more than made up for the weight of the new winglets.