As a consumer, no.  As a business owner, probably.
What most people don't realize is that most business transactions, even for IT companies, occur offline.  As a company owner, 99.99% of our business has been acquired offline.  Most of our clients haven't even looked at our website.  
That's not to diminish the value of a quality site of course.  It has its place, but many small businesses fall far short of what could be considered an standard.  
In summary:  
If it's an online retailer, I'd look for the site to be of a certain quality or at least have a lot of references.
If it's a service company, especially local, then I wouldn't give much credence to the site unless it's absolutely horrible.  I don't care that my landscaper's website sucks, because he does great work.  Our website won't rival Microsoft's, but our work speaks for itself.