From Matt Yglesias, on Taco Bell's attempt to move upscale a bit to compete with Chipotle:
It's just very difficult to simultaneously be the place people think of when they're thinking "I wish I could have a hard-shell taco with the shell made out of Doritos" and the place where people think "I wish chef Lorena Garcia would whip up some fresh flavors out of high-quality ingredients."
This is all but impossible to argue with. And speaking of fast food Mexican places, did you know that Del Taco has surprisingly good fries? Well, it does. (Though please note the low bar for "surprisingly good.")