I don't think it's that people are "mean" or less friendly than in the South--it's just harder to break through with strangers. People in general are a little less outgoing towards strangers (not sure if that's the right word, but can't think of one better) and a little more focused on their own things. That may be because the work culture is so focused--free time is a little more valuable when you're working long hours and people just may not be as willing to stop in a grocery store and chat for half an hour on the best way to cook zucchini.
I guess another way to put it would be that everyone is headed somewhere (and not always a place), whereas living in the South I remember the culture being a lot more about relaxing and waiting for things to come to you. It's not as bad as New York, where everyone is literally headed somewhere, but more like a state of mind--like everyone here is working on a difficult puzzle in their head, even when they're not at the office.
Take a trip out to Tahoe or Yosemite and that mostly shuts off--people you meet on hiking trails and in restaurants/hotels are warm, friendly, and usually pretty chatty.