It really must vary from area to area. The Taco Bells around here are super clean and top notch. I love their Nacho Supreme combos- get one once a week. BK is so-so, but I like their chili. McD's screws up my order every time, KFC has problems taking my order (their CC machine is always down, their speaker doesn't work on the drive through, they're out of chicken, etc).
I do not like Chipoltes- it's like Subway for mexican food, and it tastes like something you'd get in a gas station on put in a microwave....for just under $10 :|