Murphy started on Iams kitten for a year (all foods listed are dry). We switched to Iams adult when she was a year old. I got samples of Nutro Natural (in my Mom's dog food, of all places) and Murphy loved it, so we switched (the normal slow way). Nutro made her puke up bile. She had never thrown up in her life until we tried this food, and she continually threw up at least once a week since we switched. So, we switched back to Iams, and the problem went away.
After reading this website, I tried Chicken Soup, and again, Murphy loved it. This time, Murphy (WARNING, GRAPHIC) pooped way more often, had soft, slimmy stools which didn't come clean out of her rear end and fell off after she got out of the litter box and stunk to high heaven. She would also occasionally throw up undigested food. We switched back to Iams and the problem went away.
With Iams, Murphy has regular, solid, less stinky poo and never throws up. She has also never had a hairball in her life.