Unless they use non-square pixels, it can't be 320x480 (that's 3:2 aspect ratio, which the device clearly isn't). 480x960 is in line with the display's proportions. Here's a closeup of the screen, the resolution seems fairly smooth, 2:1 aspect ratio, no sign of discoloration caused by subpixel rendering. While the picture is not perfectly in focus so I cannot judge the exact resolution it certainly seems more to me than triple-up math.