I guess I am in the minority on this, yes i use a line on the ball, you can't convince me that the average person has a better view of the line looking down, sideways, and with one eye at a different angle than having both eyes level and behind the ball looking at the hole. Once you have it lined up you just need to worry about the speed of the putt, of course you need to hit it square, but that is true no matter how you line it up. I could be wrong, but most pro's I see putting on TV, line their putt up with a line on their ball from behind, certainly not all but a majority. In my opinion putting is hard enough, taking the 2nd guessing out of lining up your putt while standing over your ball just seems to make a difficult process easier.