In China Eastern, you are prohibited to use a smartphone during a flight, even after a leaving phase, and also even if you set it to flight mode.
In fact I saw many passangers instructed to stop using it by a flight attendant. Also, when I used my Walkman (an iPod-like portable music player), I was asked if it is a smartphone. I explained it is a walkman, and then was allowed to use it.
However, how about using a Nintendo 3DS? As the latest series of Pokemon was released recently, I definitely want to play it during my flight.