aspartame is one of the evil things I try and avoid, high fructose corn syrup is the other. It can be tough, but I find that cutting back and having 1-2 a day that is just sweetened with cane sugar does me just fine. Sure they have a few more calories but cuts out that craving. If you cut it completely out, watch out for the headaches that seem to come with stopping the drinking of diet sodas. If you want some scary info on aspartame, watch the documentary on it called " sweet misery".. It can be scary stuff..
http://www.youtube.com/watch?v=P-usbGZez40