The camera in the Xperia arc has been given a bit of a boost over the X10 on a number of fronts. For example, the sensor is more sensitive to light with a bigger aperture on the cards too. The speed of the camera has been increased too with less time between shots and Sony Ericsson claim that this will improve further before the official launch.
The interface has also been tweaked so that the user has more control over certain features e.g. the flash.
[via Sony Ericsson]