I don't eat grilled cheese, but I never thought it was particularly healthy before reading up on nutrition and experimenting with a more paleolithic style of eating, and I certainly don't now; but neither are many other restaurant chains' signature offerings. You can eat them if you like, it's your own body after all.
(Aside: My impartiality to grilled cheese is possibly also because I'm British, and you can't get a decent cheese-and-beans toastie here for love nor money; it's nothing without the beans, I say. Nothing!)