Wanted to try flying long-haul J on a Chinese carrier last year. MU SIN-PVG-JFK one-way on a single ticket.

One hassle factor early in the morning was that the airside lane for flight connections opened at 6am (or something along those lines). Unless one was interested in going via landside, it was a bit of a wait.

Furthermore, they wanted you to go via transfer desk to get your BP stamped before letting you proceed to flight connections. That was another mess.

Not the end of the world - and most probably more convenient than going via the US - but not my favourite experience.