@Justloadit
On the subject of the Ferarri - it might be overkill, but subconsciously, I might see a business owner's vehicle as a measure of how well his business is doing. Either extremes would be a cause of concern for me - if someone shows up in a battered skedonk after claiming that his company has been an industry leader for the past ten years (or something like that), I would have my doubts about exactly how successful he really is. Conversely, if someone who has only been in business for a month shows up in a Ferarri, I'd be suspicious as to how he's paying for it. I agree that you can make bad decisions if you judge a book by its cover alone, but sadly, that's what we do more often than not.

On the subject of personal appearance - you make a valid point. I wouldn't hold it against someone (e.g. a mechanic )if he has rough hands or smells of grease. As Mark said, it's situational and this is assuming that I'm seeing him in his workshop - if he comes to my premises to negotiate a large maintenance contract, for example, I'd expect him to look the part.

@Mark
Spot on! Suits might be overkill in some industries, but if someone neglects something as small as shining his shoes or proofreading his documents, I'm not going to trust him to give my professional needs the attention that they deserve. It's a case of being faithful in the small things.

@Mother
Excellent explanation! I believe that clean and tidy is a relevant term - a restaurant kitchen may have flour sprinkled all over the place and it would still be acceptable, whereas a law firm with documents all over wouldn't cut it.

@Rory
Agreed - racist remarks in particular are unacceptable.

I think we can conclude that even though we shouldn't do it, we generally judge a book by it's cover. Thus, presentation of oneself and one's business is an important factor when dealing with customers. With suppliers, everyone can judge for themselves.