I don’t think there’s a whole lot of doubt about the aircraft itself any more than regular uncertainty of any new airframe that needs time in the saddle to be proven. Airbus has competently built lots of airplanes, and this one will likely fly just fine too.
The question about the 380 is a strategic one. Airbus has gambled their future on the economic success of this plane, and they’ll need to sell a whole lot more of them if the company is to remain a going concern. With or without government subsidies if they don’t sell, they don’t sell.
The criticism of airbus’s decision to build this plane is more about whether there is a big enough market for them at this point in time, or not. Only time will tell.
My hunch is that Boeing’s decision to not pursue that market but to go after the more modest size routes with the 787. Boeing’s already sold enough planes to pay for the project and that’s without delivering a single one yet.
The (very impressive) A380 will become the plane of choice for airlines like Singapore which need large capacity aircraft, and the 747 will begin to phase out of existence. But the 787 will probably be the aircraft of choice for most international routes in ten years - the A350 XWB being too late to market to pick up much market share unless Boeing falls way behind in their delivery timetable.