There are lots of ways you can drink something tasty and not have such a huge impact on your body. Sometimes i'll buy a two-liter of green tea ginger ale or cranberry juice, and make a 50/50 or 25/75 mix of the drink and tap water.
You can also just cold-brew tea or coffee and mix in a little sweetener or other flavor to change it up. It's cheaper than soda and (after you stop drinking soda every day) tastes much better because you're not getting hit over the head with truckloads of sugars. Ask a European about how sweet all our foods and drinks are.
The thing I'm actually most worried about is pancreatic cancer. I'm not even sure if there's a link between that and soft drinks, but I read one study where having 2-3 soft drinks a week doubled your risk of getting it. Well I was having 20 a week, which scared the crap out of me. And more and more people appear to be contracting and dying of it, so it's my secret fear.
"say you have two liquids, like Diet Coke and Coke Zero. Diet Coke has a pH of 4. Coke Zero has a pH of 3. Since pH measurements are logarithmic, this means that Coke Zero is ten times more acidic than Diet Coke."
There's a whole world of drinks not found in your local vending machine that are crazy tasty and healthy for you. Fruit/vegetable-infused water, iced teas and blends, juice seltzer, kombucha, iced coffee, and about a billion delicious latin juice drinks with fruit that only people who speak spanish know about (my fav's probably Guanabana, though watered down a bit).
This article has some good explanation of the health detriments too: http://health.yahoo.net/experts/drmao/what-soft-drinks-are-d...