Trust me, I'm as anal as they come, as you can tell by the lines on my table. Its almost impossible to place the balls exactly the same from pictures. The parallax is huge, as is the distortion from the lens.
That's actually the reason I put the lines on my table. To record myself practicing, and if I come across a trouble shot in a session, go back to the video and try to set up the same shot. The lines help a lot. But still, I think even with the lines, its extremely difficult to get better than about 1" ball placement.
It would be nice to able to get a pic of the layout from directly over the center of the table looking straight down. I wonder how far above the table the camera would need to be??