Originally Posted by HPLovecraft: "If you consistently show up at work dressed sloppily but consistently do outstanding work, and your boss and co-workers are still somehow weary of your ability to do your job well because you don't have a crease in your slacks, the work-place, IMO, is bunk. They choose to look past your work and instead focus on the exterior. To me, that shows I'm working for a bunch of incompetents that are focused on flash and fluff."
Fair enough, but that assumes that your workplace is static, that these people have knowledge of your outstanding work, and that you will not interact with people you do not see on a regular basis (e.g. clients, the public at large).
Not saying that this is a hard and fast rule, but in my experience, the two tend to correlate. Not so closely that a lack of creases in pants is a predictor of slack work, but more like a consistently wrinkled shirt and dirty shoes shows a potential tendency towards carelessness.