I'm sorry, folks, but whether it should or shouldn't, your first impression does affect how people react to and interact with you, and first impressions do affect outcomes. The good thing is that times have changed and public life is generally more casual than it used to be. I think it is safe to say that it doesn't matter whether you buy your clothes at the Goodwill, Walmart, or Joseph Banks; if you are clean and dress with self-respect, you will be better received than if you are unkempt and sloppy. People are more willing to give you the benefit of the doubt.
There is a reason why you are polite, civil and respectful during a traffic stop - because it makes a favorable impression. Your attire makes an impression, too.
SentryOne, it's hard to OC without tucking in your shirt, just from a practical standpoint. As long as you are reasonably clean and neat, I don't think most people with notice or care that you are carrying. If people do notice, the better your first impression, the more lattitude you are likely to receive. We tend to be a lot more conscious of our own carry, than others are.