I don't drink pop at all anymore. In the past four or five months I've probably had about 3-4 cans total.
Now... I used to drink pop savagely. I'd have a case a week -- and that was just at my house. So that there is 3-4 pops a day, just at home. Then you factor in going out to eat: I'd always get a pop with my meals; I go out to eat a lot, and I tend to get a lot of refills. Then whenever I'd go to a buddy's house, I'd always take pop they offered me. When we'd pick something up from a convenience/grocery store, I'd get pop.
I'd say I probably had like 5 a day. Maybe more.
Then I started running, trying to lose weight... I'm not big at all -- 160 pounds, but I wanted to get into shape. I realized pop had:
a) a lot of calories
b) no redeeming value
So I quit. Honestly, I don't really think it tastes all that great. It's not bad by any means, but I don't know how I drank it so much. It makes you feel shitty.
The biggest reason for me quitting was my teeth. Although I brushed my teeth more often than most, I've had a lot of dental health. Back when I had braces, I didn't brush properly, and the spot under the braces were just obliterated with decay (while the part above/below the braces were good/fine).
The only time I'll have it is when it's virtually inevitable: like someone else said, you don't get water to accompany your popcorn at a movie theater. I actually think anything that isn't carbonated sucks with popcorn...