I spent a long 6 hours at Pudong when travelling from Seoul to Paris in June. When asked if we wanted to clear customs to leave the terminal and return, we said no since we assumed there would be enough to keep us occupied inside. But the stores and restaurants were lacking. This combined with the internet censorship made for a very boring stopover. Without Facebook and Twitter we basically spent all evening reading Wikipedia articles
I have no idea what the rest of the airport is like but I would imagine you would be better off leaving the terminal if you are there for a long time.
That being said, if it's a good deal I'm sure you will survive potentially being bored for a few hours!