A recent thread in the marketing forum revolved around suits, and their role in projecting a professional image.
I believe that your appearance alone plays a very important role - from my experience, people tend to judge you within seconds. Your conduct also comes into play - I'd be wary of dealing with someone who openly swears or makes racist remarks when dealing with a potential customer.
I'm also very finicky about documents (in terms of spelling errors, grammatical errors and poor layouts). The same logic applies to your website and your business cards.
If you drive to clients often, do you think it's beneficial to have a 'fancy' car which reflects success(I know at least two successful business owners who are of this opinion)? Even if you don't own a fancy car, it goes without saying that your car should at least be clean when visiting clients. If clients come to see you, how do you ensure that your premises project a professional image? If you're a small-business owner with a tiny, cramped office, would you rather meet your clients at a coffee shop?
What do you think about the importance of your image in business?