hope you dont mind a Qantas 400 driver adding his bit. The 380s appeal in Qantas is because the cabin is fabulous and the IFE works. It is my belief that if a 400 or any other aircraft had the new interior and good IFE it would have the same pax appeal. On an Lax/Syd service one night i followed the 380 out and compared both loadsheets. Both the 400(RR) and 380 were at MTOW. Over the sector the 380 was about 1% more fuel efficient than the 400 per KG of payload. The problem with the 380 as i see it is that as its empty weight is approx 100,000kgs heavy than a 400 you cant afford to operate it with poor load factors as the fuel burn per KG of payload will be prohibitive.