I agree, it was the hardest thing about making the switch, the after taste. About the only things I can drink are diet pepsi, diet gingerale and diet iced tea.
As far as addiction goes, I don't know what they do to diet Dr. Pepper, but it is unreal. I love that stuff, no tinny after taste and it's great. I was in heaven when I was in Cincinnati, diet Dr. Pepper in all shapes and sizes and I found it everywhere. Not so up here, only 12 oz cans and only in grocery stores. Only the occasional gas station carries single cans. No bottles to be had anywhere. This is pretty much all I drink for pop at home. Yum.