It strikes me that I should note that I'm now caffeine-free, and have been since the day after Thanksgiving. Which, by my reckoning, puts me on Day 11 of Operation Cold Turkey.
The funny thing is, I sort of quit by accident. I didn't really mean to stop drinking soda; I just sort of ran out, and then after I'd had some pretty nasty headaches for a few days I realized that I had been going without soda for a few days. By the sixth day, the headaches were pretty much gone, and I'm feeling pretty good about not drinking that stuff at the moment.
Others have mentioned that they have lost surprising amounts of weight simply by not drinking soda anymore. I'm interested to see if this proves true for me as well.