Their whole wheat buns are yummy. (Full Disclosure: one of my friends was on the product development team) They use them regularly on the grilled sandwich but you have to ask for it on the fried sandwich.
While we are on the subject, let me tell you what an amazing company it is to work for. One of my friends went to work for them a few years ago. I regularly meet her there for lunch even though the headquarters are almost an hour a way. They have the most amazing cafeteria -- full of regular chic-fil-a food as well as MANY other choices (salads, entrees, desserts, milkshakes, whatever). And it's all FREE. That's right. Totally free for employees and GUESTS!
One reason is to test food. We ate many versions of the wheat bun before they settled on the current one. Last time, they were testing different Chicken Salad Sandwiches. Another reason is that they encourage your family and friends to come see you at lunch - it contributes to work life balance! They also have almost free daycare, a free gym, the most amazing campus with walking trails. They own several beach vacation condos (not on sowal though!)that they give to employees -- you get a free week every few years. I swear if it was any closer to my house, I would work there. My friend will never leave.