It was the coffee that did it for me, too. Strong enough flavor, stronger than even the tobacco flavors, I would say, but enough of the, "Oooh, yum" factor that made me think, "This is better than cigarettes."
My mom is going through the same thing right now, except she's not using the e-cigarette consistently. She hadn't even used it, as far as I know, until a couple nights ago, when she came up to me and said, "I'm thinking about going and buying a pack of cigarettes." I told her to puff on her e-cig for 10 or 15 minutes first, and if she still wanted one after that, she could go get some.
Even with 0mg carts, she didn't want a cigarette after that.