Just flew into PVG last week, MU-MU transfer and both ways, the "International Transfer" desks and security check was closed, and had to pass through immigration. The officer will pass your PP off to another officer and he quickly stamps you in with a transit stamp. You then need to go back upstairs and clear security and exit immigration again before re-entering the terminal.
Both ways, immigration was quick (<5 minutes), but I had a 20+ minute wait for exit-immigration and the security check when entering the terminal.
One way, I had a 6 hour stop, so I went into the city for lunch. The maglev will cut some time, but even around the Longyang Road station where it terminates you still need to take the metro to better parts of the city to get real food.