Nintendo 3DS is a major improvement over their previous DS consoles. It comes with support for 3D visuals.
And considering it requires more processing power to handle the effects, the device is going to run down battery faster.
Nintendo too has confirm the same. The company has stated that Nintendo 3DS would require more frequent recharges compared to the previous DS devices.
They are going to bundle the unit with a charging cradle to make it easy for the gamer to keep his unit charged up.