I do not use medicated feeds, period.
However, I do lose hens and broilers to coccidiossis which could have been prevented using medicated feed. It's a decision we made.
The only sustinable solution, in the long run, is to let sick animals die and then breed the ones who were unaffected by the coccidiossis. They then past their natural resitance along to their offspring and I'll have a more vigorous flock in the long run.
But, it's hard love. It's never good to find a dead chicken... but if I were to bring in day old chicks every year as replacements the cycle would just continue on ad nauseum.
[edit] Let me add, I do treat my goat kids with Albon, since they are not intended as meat animals. So when I say I don't use medicated feeds, I do not. BUt I do treat the goats. The lambs I only treat if they actually get sick and I verify cocci through a fecal. I'll then market them separate from my "antibiotic free" meats.