"Overall, Americans consume too much added sugars from all sources. Estimates reveal added sugars represent 16 percent of calories (that’s an average of 300 to 400 calories) or 21 teaspoons of added sugars per day. These calories offer no nutritional value. "
Empty calories that pump up your insulin response and promote fat storage.
As said earlier treat it as a replacement for dessert not water...it is after all liquid candy.
I never buy soda myself but have some sometimes when at my dads house since he still drinks it, he has cut back a decent amount at least.
edit: and if anyone wants to kill time with a sugar documentary, this is pretty interesting: