For those who are not Americans: how true do you find the "ugly American" stereotype to be?

I’m interested in your personal experience with Americans. How do you think we tend to behave when we’re visiting you? I am asking for both generalizations, but also specific cases that differ from the generalization.

Do you find Americans tend to be defensive? Haughty? Do we make a lot of assumptions that we shouldn’t make? Have you met Americans who are respectful, interested, and courteous? What do you think explains the difference between the boors and the decent ones?