Honestly I believe there's a puritan streak in the aspartame controversy; you don't deserve to experience sweet taste if you're trying to avoid sugar, you need to suffer for your diet, and it's unfair to have a zero-calorie soda that tastes good.
I could be convinced otherwise by data, but when I'm seeing decades of attempts to prove it's dangerous and none actually pan out, I'm not going to feel bad about drinking a few diet cokes a day.