Dear kali,
I am certain, based on my personal experience, the advice of neurologists at Beth Israel in Boston, and my local physicians that aspartame is damaging. I think it's addictive as well, since people seem to have a very hard time stopping using it.
Why don't you try stevia in your morning coffee and switch to naturally flavored seltzer water for a cold treat.
Aspartame appears in a lot of food, nutritional and even medical products, like cough syrup. Anything "low-calorie" or "sugar-free" gets a very careful label reading.
Love, elephant