Even if they don't reach a deal Obama won't let the US default. Unless he's just the worst President ever, which I don't think he's that bad. But they'll reach a deal shortly after if they go past the deadline. I think they still have several weeks before an actual default would occur.
It's just negotiation. It's what they do. The fearmongering is a part of it. What the republicans are asking for now is extremely reasonable. I think most Americans would support the GOP's latest offer if they cared to know what it was. I don't really get what's wrong with negotiating, but some people can't stand the heat.
People will get all worked up over it next time too, but they'll always raise the debt ceiling before default or before we get too far into default. They have no choice.