I don't know about Heathrow-5 but I can tell about Beijing-3, and I think everyo...

I don't know about Heathrow-5 but I can tell about Beijing-3, and I think everyone telling it's a great airport has no clue. The flows are terrible, you often board at the farthest gate away, sometimes by buses, even though most of gates are empty, and most of the airport is empty (the middle part is still closed but the international part is further away). The customs bottleneck is the worst ever, it's not uncommon to wait 45mins, there's like 12 counters for all international arrivals. The building does actually look like the bottleneck, and it is. The waiting areas have nothing special, and they certainly feel old for a 2 years old airport. Some of the duty-free shops looks untouched since the 80s.. The roof already starts to fall apart, there was some parts ripped off by the wind lately, and there's concern about the build quality.

And well, it's unfair to compare cost and construction time, one was built by thousands of workers, working 24/7 for a minimum wage, the other... And btw, Beijing T3 was designed by a dutch consortium and a British architect.