At my office I try to dress decently enough to seem more-or-less "professional": a conservative shirt, slacks instead of jeans, etc. But above the collar I'm pretty scruffy-looking --- probably one of the top 0.1%, if not the absolute champion, in unkemptishness of hair and beard.
Perhaps I'm naïve, but I've always felt that the things that should count are one's creative ideas, relevant skills, productive behaviors, collaborative talents, and general willingness to get the job done. Looks should be utterly irrelevant. So should race, sex, religion, speech style, etc.
But of course, that's in an ideal universe. In real life, to be taken seriously one has to adapt to one's environment. Protective coloration is occasionally needed, especially to overcome barriers of prejudice, perhaps more often during interactions with outsiders or members of older generations. Women seem particularly vulnerable in this Darwinian competition, at least in today's corporate culture. A comrade who is quite short found that she wasn't respected in her mainstream occupation; she had to become a technologist to locate a niche in which she wouldn't be dismissed due to an at-first-glance somewhat childlike appearance. Another friend had to adapt a uniform of skirt and business suit; if she wore pants people assumed she was a clerical worker. And many younger women find it necessary to disguise any feminine characteristics, lest they be leered at and categorized as bimbos or worse.
So I've come to believe that my minor personal scruffiness is a tiny public service --- it at least may make a tiny contribution to pushing the envelope, opening doors, and broadening the bell curve of expectations in the organization. I do admit to wearing a coat and tie, back around 1989-91 when I was a mangager for a hellish 18 months. And I'm willing to bend my principles if there are foreign dignitaries or other august and inflexible personages visiting ... though come to think of it, I can't remember any such for at least the past decade ...