Two years ago the thing that bothered me most when I was homesick was missing home. Now I'm bothered more by the detachedness. For the first year my friends operated under the assumption I was imminently coming home. They don't anymore, which is fine, and I'm certainly less relevant to some of them now (though not the closest ones). The Internet helps, I probably wouldn't have lasted so long over here in the days before Skype.
Luckily, I think I'm going to make it home for a week or so at some point in the next three months. I'm feeling overdue.