I drink primarily Zero, I switched to it at the same time I ditched sugar in favour of artificial sweeteners (I tried to drink tea without any sweetening but gave up after few weeks, I just can't stand it). It's wonderful where I live (Poland), and I grew to like it even more than plain Cola. I've also seen numerous attempts to promote Zero over the original flavour; one time they even gave away cans of Zero disguised as ordinary Coke to make a point (you had to remove the can from a cardboard overlay it was in to discover it's Zero). I don't know how successful were those campaigns though.