I've hardly ever eaten red meat in my life, because growing up my parents were both vegan and it was never in the house.
I think the last instant where I decided to become vegetarian was when I was in a restaurant with my usual plate of prawns and pasta (I used to *love* prawns and shrimp) and I stopped and realized that each prawn was like a whole animal. And that made me feel strange. Since then, I basically haven't eaten any animals. For a short time, a few years ago, I tried to get used to eating fish and/or poultry again because I was under the delusion that I wasn't getting enough protein (I had become underweight for the wrong reasons... complicated story).. but I didn't like it. I didn't know how to make anything, because I've never done that for myself.
So, for me, I guess my tastes haven't changed because they were never there in the first place.
I do notice, however, that I have different tastes than other people. I used to LOVE cheesy pizza, but I look at it now and it looks like a greasy mess. I even remember when I was a young kid, I wouldn't eat salad and would fight with my parents every night when they prepared it for me. Maybe I was just being stubborn, or a just *being a kid), but now I love salad... if it's well prepared, anyway.
Another thing is that for a while I had cut out tall soda (now I have diet soda sometimes, though), and I remember when I drank it again, my stomach would get cramps from the carbonation or something.
(sorry for a bit of rambling
)