I used to drink Country Time Lemonade like it was water. Not just straight CT, but with extra sugar on top of it. Before that it was Lipton Iced Tea, also heavily sugared. When I quit the stuff, within months I had lost 20 lbs, then 30, then another 5 lbs over the next couple of years. I do drink soft drinks, but always the diet variety (sweetened with aspartame or sucralose, I can't stand acesulfam-K or saccharin), and I avoid sugar in all its forms. Because I don't like the taste of most straight water and refuse to pay for bottled water, I use diet powdered drinks like Crystal Light and similar grocery store knockoffs now, instead of CT.
I've kept that weight off for 12 years and haven't seen any tendency to gain it back, though I did gain 2 lbs recently which I consider a wake up call that I do need to be careful with portions. As Mari said, everyone reacts differently and some people may tend to gain weight from consuming artificial sweeteners. For others, they live up to their billing with no negative side effects.