Actually I borrowed someone’s newer phone and I can see a white space appearing after the image has slid across. It’s just a flash and then it’s gone.
My first thought was that perhaps the images need to be preloaded but even on a second cycle the flash is evident.
The iphone 4 on the other hand is fine.
I’m not on a computer at the moment so can’t do more tests but I will take another look in the morning if no one else has jumped in.
Also I note that you are not putting the natural width and height attributes into the image html so the browser has to load the image first before it can work out the aspect ratio to resize it (which you do in the css). If you supply width and height attributes it speeds up that process even if you are later resizing with css.